Monster Oatmeal Chocolate Chip Cookie Bars.
Tuesday made better with Monster Oatmeal Chocolate Chip Cookie Bars for snacking. These one bowl homemade oatmeal cookie bars with chocolate chips and Reese’s Pieces are the perfect way to use up any leftover Halloween candy. They’re super easy, festive for both Halloween and Thanksgiving, and most importantly, everyone LOVES them!
It’s been so long since I shared a simple cookie bar. But with Halloween right around the corner, I figured now was the perfect time.
We don’t get trick-or-treaters up here where we are, it’s a little too rural. Asher goes into Frisco where she goes to school and where the businesses on Main Street hand out candy. But she never brings much, if any, home. In general, we really don’t eat candy, and I don’t usually love using candy in my baking recipes. But sometimes, mostly for fun holidays like Halloween and Christmas, I cave in and throw some candy into recipes.
The Halloween candies that we always have a lot of around here…M&M’s and Reese’s Pieces. I tend to buy way more than we’ll actually ever eat. I get so excited when they come out with the fall colors…followed by the holiday colors (I’m such a sucker for any kind of holiday packaging), that I buy one too many bags and never know what to do with them all.
Enter these cookies bars. I mean, it’s Halloween, so I figure, if there’s ever a time to have fun with a candy filled recipe, it’s now. You know?
A simple oatmeal cookie base studded with chocolate chips and your favorite leftover Halloween candy. I used Reese’s Pieces, but M&M’s or your favorite chopped up candy bar would be great too. Use what you, your family, and friends love most.
As you can guess, these are pretty easy to make.
I used my mom’s oatmeal chocolate chip cookie recipe as a base (which is from the HBH cookbook). Then I stirred in some candy pieces (again, use your favorite, chopped Reese’s would be so good too). I also decided to bake the cookies into bars, instead of round cookies. Mom’s recipe is honestly the BEST. Nothing beats it, and the fact that it’s a one bowl and done kind of recipe makes them that much better.
Bonus? I pretty much always have the ingredients on hand. So it’s the perfect recipe to bake up whenever a craving for oatmeal cookies hits. And yes, along with this bar being easy to make, they’re also so delicious. Best oatmeal cookies. Ever.
And I really mean it.
I baked these up with my little sister, Asher in mind. She’s been begging me to make cookies. She has a class Halloween party coming up that I promised to bake something for, so we tested these cookie bars out over the weekend. These are full on Asher approved. The thing with kids? They tend to be picky, so I knew I could be getting into trouble with the oatmeal cookie. But I really wanted to bake up something other than just another chocolate chip cookie. Been there done that. I was worried, but when she came down to the studio on Saturday, she ended up loving every bite. She could not get enough.
Granted, she loved the “Halloween” colored candies. But she also said the cookies were delicious. She’s so excited to make them again for her Halloween party.
Side Note: Asher is now ten. When I asked her what she was going to be this year, she said, “you’ll have to wait until Halloween to find out”. And with sass. Ugh. I wish she’d just stop growing up already!
Whenever I make the recipes I grew up baking with my mom, those more classic recipes, I always ask myself, why don’t I bake these more. Obviously it’s because I am constantly testing out new recipes. But it’s a bummer that it’s hard to find time to bake anything that’s “old” and from the archives. I’m glad I decided to dust this recipe off and share it with you guys.
Sometimes I forget that it’s the classic recipes that are really the greatest. Hands down a favorite recipe of the month. And I love that these are fun for both Halloween and Thanksgiving.
If you make these cookie bars please be sure to leave a comment and/or give this recipe a rating! Above all, I love to hear from you guys and always do my best to respond to each and every comment. And of course, if you do make this recipe, don’t forget to also tag me on Instagram! Looking through the photos of recipes you all have made is my favorite!
Nutritional information is only an estimate. The accuracy of the nutritional information for any recipe on this site is not guaranteed.
Monster Oatmeal Chocolate Chip Cookie Bars
These one bowl homemade oatmeal cookie bars with chocolate chips and Reese's Pieces are the perfect way to use up any leftover Halloween candy. They're super easy, festive for both Halloween and Thanksgiving, and most importantly, everyone LOVES them!
Ingredients
- 2 1/2 cups old fashioned oats
- 2 cups all-purpose flour
- 1 cup brown sugar packed
- 1/2 cup granulated sugar
- 1 teaspoon baking soda
- 1 teaspoon salt
- 1 cup canola oil
- 2 large eggs
- 1 tablespoon vanilla extract
- 1 1/2 cups semi-sweet chocolate chips
- 1/2 cup Reese's pieces or M&M's
Instructions
-
1. Preheat the oven to 350 degrees F. Grease a 9x13 inch baking dish with butter or line with parchment paper.
2. In a large mixing bowl or the bowl of a stand mixer, mix the oatmeal, flour, brown sugar, granulated sugar, baking soda, salt, canola oil, eggs and vanilla. Beat until the dough is moist and all the ingredients are combined. The dough will be crumbly. Mix in the chocolate chips and 1/4 cup candy pieces.
3. Press the dough into the prepared baking dish and scatter the remaining 1/4 cup candy over top. Transfer to the oven and bake 18-20 minutes or until the edges are set and the bars are golden. Let cool and then cut into bars.
Our Favorite Recipes
Instant Pot Turkey Meatballs and Spaghetti Squash.
So nice you made these with Asher! And Reese’s Pieces for the win.
Yum, looks and sounds delicious. I love how colorful these are! 🙂
“and with sass” – I’ve said it before and I will say it again – I’m pretty sure Asher is my spirit animal!!
Rebecca | http://www.peppermintdolly.com
Looks very good.
Bealtiful and delicious
Wish you could give carb counts. I have a grandson who would love these but is only allowed 30 carbs for dessert
Omg. Your blog and recipes are so dangerous. I can’t open a blog post without NEEDING to make your recipe. Pinned this, can’t wait to try!
This is such a creative way to use up leftover Halloween candy! We don’t get trick-or-treaters where we live, but my parents usually do so I think we’re going over to their house to hand out candy and see all the cute costumes 🙂
Thank you so much Sarah! That will be so fun to go over and pass out candy! I hope you have a great time!
hey girl- these bars look oh so yummy!
Thank you Shawnna!
I’m an American in Australia and Reese’s pieces aren’t readily available here, especially at US prices. Could I swap in a tablespoon or two of PB to get the peanut butter flavour? These look awesome, I’m keen to make them for my work team for Halloween!
HI! I would swirl the peanut butter into the dough, don’t mix it in or the cookie might turn dry. Swirls will be so good! Please let me know if you have any other questions. I hope you love this recipe. Thanks so much! xTieghan
Can you use quick oats instead thanks
HI! I don’t recommend using quick oats as they will cook up differently. Please let me know if you have any other questions. I hope you love this recipe. Thanks so much! xTieghan
OMG these look REALLY REALLY YUMMY! I’m going to make these today. Can I make these into round cookies??
Hey Debbie! Yes, you can bake these into round cookies. That works great! Please let me know if you have any other questions. I hope you love this recipe. Thanks so much! xTieghan
Do you alter your recipes for high altitude? We love here in Breck and baking can be so frustrating.
Hi Dea! My recipes should work great at your altitude! I hope you try these!
@ Patricia Hale, he could have a SMALL square of these, as the entire bar would be well over 30 carbs. Interesting that he has a limit for dessert, given the number of carbs a person eats in their regular food throughout the day varies so significantly. There are recipe builders all over the internet, so you can plug any recipe in to one of them and get a carb count for yourself. Teighan doesn’t do nutrition content on her site, but a number of sites do. I recommend cookieandkatecom and chocolatecoveredkatiecom. I’ve seen nutrition links at the bottom of their recipes. Plus, the goal of their sites is more nutritious sweets using less sugar, whereas this site is just a REAL GOOD cooking blog. Good luck!
Thanks so much for this awesome info, Renee! Really appreciate you being so generous with your suggestions and your kind words! xTieghan
These are fabulous!!! We made them the day you posted them. I’ve been disappointed by cookie bars in the past but these are divine!!
Thank you so much Heather! I am so glad these turned out amazing for you!
I live in an apartment on my university campus, so I am certain we won’t be seeing any trick-or-treaters anytime soon. In my opinion, that’s a GOOD thing because I don’t have to share ANY CANDY. HAHAHAHA. But in all seriousness, this recipe is divine! I’d prefer this over candy any day given that I like my desserts comforting and hearty. It’s so easy to down so many peanut butter cups and chocolate in a sitting. NOT EVEN FUNNY.
Thank you so much Cassie! I am so glad you like this recipe and I hope you have an amazing Halloween!
Hi I made ur lovely recipe but I used raisins instead of chocolate. (What I had in the house) I also subbed 1/2 cup raw stevia for the 1/2 cup white sugar, so I’m sorry to ask. Substitutions do not guarantee a perfect recipe, I know. They taste great but won’t hold together well to cut bars. What should I do differently next time? Another egg? Thank u!
Hi! So my guess is they are not holding together because of the stevia. I don’t love baking with stevia and have had issues with it in the past, so that’s just my guess! Not sure how to correct the problem as I have not tested the recipe that way you have made it. Sorry I could not help more, but glad you are enjoying the bars. Thanks so much! xTieghan
I love these bars, what a perfect Halloween treat!
Thank you so much!
these look delicious – i love monster cookies and anything reese’s so i’ll definitely be making them soon! i hate to be “that person”, especially because this is a dessert so you *shouldn’t* be eating a ton of it, but 1 cup of oil seems like a lot. any suggestions for another liquid? maybe a half oil, half applesauce kind of thing?
Hi! You can use 1/2 oil and 1/2 applesauce. While it is not quite the same, it’s still pretty good. Please let me know if you have any other questions. I hope you love this recipe. Thanks so much! xTieghan
can you make these with butter, or a combo of butter and oil?
HI! You can use melted butter, but I do like oil best. Please let me know if you have any other questions. I hope you love this recipe. Thanks so much! xTieghan
could a different oil be used instead of canola? Coconut maybe?
HI! Yes, you can use melted coconut oil, though I prefer canola oil. Please let me know if you have any other questions. I hope you love this recipe. Thanks so much! xTieghan
can I substitute the oil
for the coconut one?
HI! Yes, you can use coconut oil, but I do prefer canola oil. Please let me know if you have any other questions. I hope you love this recipe. Thanks so much! xTieghan
Could you freeze these? Would you bake then freeze or freeze raw and bake?
HI! I have never frozen cookie bars, so I am not sure for sure. I would freeze after baking and then thaw on the counter. Please let me know if you have any other questions. I hope you love this recipe. Thanks so much! xTieghan
I made this and love it! So perfect for a fall potluck. The Reese’s are great fall colors. I baked this at about 5200 feet and probably should have cut down my baking soda slightly and upped the temp to bake, but they still came out wonderfully!
Thank you!
I am so happy to hear that! Thank you so much Nicole!
These were a hit at my work’s Halloween potluck lunch! Definitely recommend.
YES! So happy to hear that Jenna! Thank you!
made this yesterday… and it taste greatttttt… Marvelous.. my new fav oatmeal dessert/snack … not good looking as yours but tasty 🙂 you got a new fan
I am so happy to hear that! Thank you Micheal!
I made these the other day and they were fantastic! So easy and so delicious. I really like the texture of the oatmeal giving it a nice chew and the bar was not dry. Thanks for creating and sharing so many awesome recipes!
This is so sweet! I am so glad you loved these bars, Melissa! Thank you!
Loved these! They were super simple and perfect to bake up on Halloween and share with friends! I am excited to do the same around Christmastime with seasonal M&Ms 😀 This is a great option when you want a great homemade treat, but don’t have a lot of time. Thanks!
Thank you so much Lisa! I am glad these turned out amazing for you!
These cookies were a hit. They couldn’t have come together easier (I think from the time i started baking, it took ten minutes to get them into the oven) and everyone who tried them loved them. I used quick oats instead of traditional oats because that’s what I had, and they turned out just fine– probably less chewy, but the cookie texture was perfect and they held up fine. I can see myself using this recipe time after time and using seasonal M&Ms for various holidays. Thank you for the great recipe!
Thank you so much Caitlin! I am so glad you loved this recipe and hope you love others on my blog as well!
Made these this week and they’re AWESOME! Simple yet decadent and yummy. I ended up needing to cook mine for several more minutes than you suggested to get them cooked through but maybe my oven is weird. Either way, another WIN from Half Baked Harvest 🙂
I am so glad you loved these bars, Kate! Thank you!!
These look DELISH! They remind me of something my mom used make when I was growing up! (:
Awh I am so glad these brought a good memory to you! I hope you try these, Macy! Thank you!
Would olive oil work? Canola oil is such a toxic oil so I avoid using it.
Hey Wnedie, If you don’t like canola oil I recommend using melted butter or melted coconut oil. Please let me know if you have any other questions. I hope you love this recipe. Thanks so much! xTieghan
I made these tonight! They taste delicious, but they fell completely apart. I don’t know what I did wrong
Hey Penny! Any details about how you made this would be helpful. IN general this is a very crumbly cookie bar, so you might not have done anything wrong. Please let me know if you have any other questions. So glad you love this recipe. Thanks so much!! xTieghan ?
This is seriously one of the best cookie recipes ever, I put peanut butter m&m’s in with the dark chocolate chips and everyone loved them. Thanks so much for sharing! I am going to attemp to make them into round cookies tonight to make them easier for giving/sharing. I hope I don’t mess them up!
I am so glad everyone loved these, Cherie! Thank you so much!
These are so good! I wasn’t so sure after mixing them up and they were all oily, just a different look/texture than I’m used too (most cookies use softened butter and so blend differently). I baked them for 5-10 minutes longer than the recipe. My kids and I loved them. I love the chewiness of the oats and the chocolatiness of the chips. Thanks so much!!! P.S. I’ve wanted to try them for months now!
I am so glad you all loved these Nicole! Thank you so much!
Great base recipe – so versatile! Thanks for sharing!
Would never have thought the oil would churn out such a good bar cookie 🙂
For the record I used half coconut oil/veggie oil (it’s what I had), and added shredded coconut (didn’t have any m&ms or Reese’s) – absolutely delish! Will make again.
Bonus? The fastest cookie prep ever.
I love to hear that Rose! Thank you for giving these a try! xTieghan
These are fantastic! I was a bit skeptical of the oil as I prefer to bake with butter but I am no longer a skeptic. I used peanut butter chips in place of the candies only because I did not have them in my pantry. These were a breeze to make and stored well too.
Thank you so much Mossy! xTieghan
These are delicious! I made and took out all the candy (sorry) and added crans and chopped apples and a teaspoon of cinnamon. Nice fall treat!
Thank you so much Ann! xTieghan
These were great and whipped up extremely quickly! Perfect for a treat to have around when a sweet craving hits. I did find the baking time was way off, mine ended up taking about 35 minutes.
I am so glad you enjoyed this recipe! Thank you so much Erin! xTieghan
Hi there:
Does this freeze well baked and unbaked?
Hey Jennifer! These bars freeze well once bake, wrapped up tightly for up to 3 months. Please let me know if you have any other questions. I hope you love this recipe! Thank you! xTieghan ??
Question about time in oven. The note for this recipe in your book says to bake the bars for 25-30 minutes, but the online recipe here only says 18-20. Which is correct?
Hi Ryan, this is a different recipe from the one in my cookbook. You should follow these directions for this cookie bar and bake 18-20 minutes. Please let me know if you have any other questions. I hope you love this recipe! Thank you! xTieghan
These bars are amazing! I didn’t have reeses pieces so I used mini M&M’s and they turned out great! I made them for our family vacation to Hawaii and our kids and kid around us devoured them! My husband loved them too! This is now a bi-weekly staple for lunches at school! Thank you! I probably sent your recipe to 20 people!
I am so glad you loved these! And thank you for passing them along! I hope you had an amazing time in Hawaii! So fun! xTieghan
Thanks for the great recipe! I halved it and used 3/4 Cup mini chocolate chips and 1/2 Cup mini m&m’s mixed in, I didn’t need to save any to top it, they showed through just fine. I cooked it in an 8×8 for 25 minutes and it was perfect and delicious!
Thank you so much Amanda! I am so glad you loved this! xTieghan
HI Could I use butter instead of oil??
Hi Jennifer! Yes, you can use melted butter, but I do prefer to use oil! I hope these turn out amazing for you and please let me know if you have any other questions! xTieghan
These are delious!!!!!! Easy recipe
Thank you Shantai! xTieghan
Could you add peanut butter without messing up the recipe?
Hi Jenn,
I haven’t tested this with peanut butter, but you could add 1/2 teaspoon dollops at the end. I hope you love the recipe, please let me know if you have any other questions! xTieghan
I took your advice and added teaspoons of pb when there was about 5 minutes left to bake. They turned out AMAZING!!!! Thank you so much!!!
Thank you Jenn! I am so glad this recipe turned out so well for you! xTieghan
Can I use rolled oats instead of old-fashioned oats?
Hey Katy,
You will want to use old fashioned oats for this recipe. I hope you love the recipe, please let me know if you have any other questions! xTieghan
Will this work with gluten free flour?
Hi Kelli! I have not tried these with GF flour, I am sorry about that! If you try, please let me know how it turns out! xTieghan
Hi! My husband and I basically only make your recipes! Loved how easy these were. However they didn’t hold together, completely crumbly. I didn’t make any substitution and I cooked a little longer just in case. Not sure what happened!
Would be delish on ice cream to eat with a spoon!
Yes! I am really glad you enjoyed these bars, Jamie! Thank you! xTieghan
These were super easy to make and tasted awesome! I took them to a dinner party and they impressed everyone there! I halved the recipe and baked in an 8×8 pan, and it worked well.
Thank you Maddy! xTieghan