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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!

overhead photo Monster Oatmeal Chocolate Chip Cookie Bars with mini pumpkins in photo

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.

close up photo of Monster Oatmeal Chocolate Chip Cookie Bars

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.

over head photo of Monster Oatmeal Chocolate Chip Cookie Bars with knife and mini pumpkin in photo

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!

overhead close up photo of Monster Oatmeal Chocolate Chip Cookie Bars

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.

overhead photo of Monster Oatmeal Chocolate Chip Cookie Bars with cookies missing from photo

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!

Monster Oatmeal Chocolate Chip Cookie Bars

Prep Time 10 minutes
Cook Time 20 minutes
Total Time 30 minutes
Servings: 18 cookie bars
Calories Per Serving: 1732 kcal

Nutritional information is only an estimate. The accuracy of the nutritional information for any recipe on this site is not guaranteed.



  • 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. 
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horizontal photo of Monster Oatmeal Chocolate Chip Cookie Bars with mini pumpkins in photo

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  1. How many days do these taste fresh for? I’m trying to forecast a long to do list prior to a weekend of food prep for fall camping and if I can make these in advance it would help me!

      1. 5 stars
        Great recipe! We love monster cookies and this recipe is great because you don’t have to cream the butter and sugar. It mixed up great and tastes Yummy! This is a great base recipe for all kinds of mix ins; nuts, toffee chips, pretzels or mini marshmellows! Thank you

  2. 5 stars
    Always make one of your recipes and the results are incredible! Here in Brazil, we don’t usually prepare bars, but I always see them here and they seem suitable for benefits in which many recipes are made, as they are practical, just cut and serve! I chose this recipe for my birthday, because some friends would bring their little children and the bars are colorful! It was a great success! We love it! Thanks for sharing amazing recipes!

  3. 5 stars
    I made these for a party and they came out great! Everybody enjoyed them. I was a bit nervous to make them based on some of the prior comments, but I didn’t have any problem with them crumbling. I baked them for 25 minutes. I wonder if the people with the crumbling problem overbaked them? My only problem was that the candies on top fell off when I was cutting them, and I had even pushed them down into the bars before baking. I had a coupon for M&M’s so I used peanut butter M&M’s instead of Reese’s Pieces, and they were a little larger, so maybe that was the problem. Anyway, they were great!

    1. Hey Amy,
      I appreciate you making this recipe and sharing your feedback, so glad to hear that they turned out well for you! xT

    1. Hey Gabrielle,
      Yes, you could use an equal amount of melted butter. Please let me know if you have any other questions, I hope you love this recipe! xx

    1. Hey Katy,
      It might be per batch! I always recommend that if the nutritional information is important to you, you use your own personal calculator. Ours is automatic and controlled by google. It’s not something we’d prefer to be using. We are required to. I’m sorry for the trouble, we do our best! Hope you enjoy the recipe! xT

  4. 5 stars
    Excellent bar cookie. I baked in parchment paper pan with overhang and lifted completely cooled bars out of pan for cutting. I had no problem with bars holding their shape but did cut bars in about 1″ x 2″ each. So much easier to cut when out of pan. Loved that recipe uses canola oil verse butter. Thanks for a great recipe!

  5. 4 stars
    Easy to make, and taste great, but I would NOT recommend making these for a gathering/classroom/work function. They do not hold their bar shape at all, and really need to be eaten with a spoon. They are quite messy if you attempt to hold them – they disintegrate in your hand. The only binding ingredients here are oil and egg, and oil does not provide structural integrity.
    I’ve made them twice and enjoyed them but will probably try something else next time, as when I make bars it usually is for a group event.

    1. Hi Robyn,
      Thanks so much for making this recipe and sharing your feedback! So sorry these have been falling apart for you, they are a delicate bar:) xx

    1. Hey Kristy,
      Awesome!! I am thrilled to hear that this recipe was a winner, thanks so much for trying it out! Have a great weekend! 👻

    1. Hey Nicki,
      Awesome!!🤩 I truly appreciate you making this recipe and sharing your review and love to hear that it was a hit! xTieghan

  6. Hi Tieghan, just made these & they came out great! Just wondering – do you think the vegetable oil can be substituted for coconut oil?

    1. Hey Krysten,
      Perfect! I appreciate you making this recipe and sharing your feedback, I am so glad it was a hit! Yes, coconut oil would be great! xx