Monster Cookie Bars
Published 5/28/2023 • Updated 10/31/2024
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These flourless monster cookie bars are made with oats, all-natural peanut butter, M&M’s, and chocolate chips, making them the perfect sweet treat. Enjoy!
Welcome to our take on monster cookie bars! They’re part monster cookies + part cookie bars mashed together and baked to chewy dessert perfection. These make a big batch — aka they’re a great sweet treat to bring to a gathering or snack on the go with the fam.
PS: you have to try our Monster Cookie Protein Balls!
What are Monster Cookie Bars?
Monster cookie bars are like monster cookies but in bar form. They’re made from the base of oatmeal, peanut butter, M&Ms, and chocolate chips.
We all love a good monster cookie here in the Midwest, and this recipe is basically one giant cake pan of monster cookies baked and then sliced into bars. Does it get more delicious!?
Why you’ll love them!
They’re Flourless: These monster cookie bars are flourless and gluten free thanks to the quick-cooking oats.
All-Natural Peanut Butter: We’re big fans of using all-natural drippy peanut butter with one ingredient – PEANUTS, and none of those extra fillers you often find in many nut butters. Smucker’s All-Natural is our go-to.
No Granulated Sugar: Instead of using white granulated sugar like many cookies and cookie bars do, we use light brown sugar for these cookies. Feel free to sub 1:1 for coconut sugar if that’s your jam!
Dark Chocolate Chips and M&Ms: We love the taste that dark or semi-sweet chocolate chips give these bars (instead of milk chocolate chips). We also used M&M’s to give them some deliciously chocolatey crunch. They’re monster cookies after all! What else could you use?
- Butterscotch chips
- Peanut butter chips
- White chocolate chips
- Raisins
Try it!
Flourless Monster Cookies
These flourless Monster Cookies are your new favorite dessert! Made with oatmeal, peanut butter, chocolate chips and M&M’s, these cookies are jam-packed with all the good stuff.
What You Need for Monster Bars
These monster bars pack a short list of ingredients you likely have on hand already. Here are the 9 ingredients you’ll need, and a few pro tips for ingredient substitutions you may be thinking of making:
- Quick-cooking oats: we DO NOT recommend using anything besides quick-cooking oats in this recipe. We found that rolled or old-fashioned oats soak up too much of the wet ingredients and result in dry bars.
- All-natural, drippy peanut butter
- Maple syrup
- Melted butter: we do not recommend subbing out the butter for another fat, as we haven’t tested it.
- Eggs
- Light brown sugar: feel free to sub 1:1 coconut sugar if you prefer!
- Baking soda
- M&Ms
- Semi-sweet chocolate chips
How to Make Monster Cookie Bars
For the full recipe, scroll down to the recipe card for a list of ingredients and instructions.
Preheat & Prep
First, preheat the oven to 350ºF and spray a 9×13-inch baking dish with cooking spray.
Mix Ingredients
One great thing about these bars is you don’t need to mix the wet and dry ingredients separately. One bowl, baby! Add to a large bowl:
- oats
- peanut butter
- maple syrup
- melted butter
- eggs
- brown sugar
- baking soda
And mix with a wooden spoon to combine. The batter should be thick like cookie dough. Then, add in the M&M’s and chocolate chips, and mix again. Mixing the M&M’s and chocolate chips in last will ensure that they’re not melted by the warm melted butter.
Transfer Dough to Baking Dish
Transfer the monster cookie dough into the baking dish, and use your wooden spoon (or hands) to press the batter firmly and flat into the dish.
Bake
Bake at 350ºF for around 17-20 minutes or until the sides begin to turn golden brown and it is firm to touch in the middle.
Let Cool & Enjoy!
Let the monster cookie bars cool for at least 30 minutes to 1 hour before slicing and serving. This will allow them time to fully cool and ensure a clean cut of each individual bar. YUM.
Storage
Let the cookie bars cool completely. Then, transfer them into an airtight container or gallon-size bag and store in a cool, dark place for up to 5 days. If your sheet pan has a lid, feel free to keep the monster cookie bars right in the sheet pan for storage.
Can I freeze monster cookie bars?
You have two options when it comes to freezing these monster cookie bars.
Dough –> Wrap dough in plastic wrap and then place in a freezer-safe gallon-size bag. Remove as much air as possible and freeze for up to 3 months.
Cookies –> Let pan of monster cookie bars cool completely, cut into individual bars and then transfer into a freezer-safe gallon-size bag. Remove as much air as possible and freeze for up to 3 months.
Monster Cookie Bars
Ingredients
- 4.5 cups quick-cooking oats, gluten-free if desired (rolled oats works too)
- 1 cup all-natural drippy peanut butter
- 1/2 cup maple syrup
- 1/2 cup butter, melted
- 2 large eggs
- 1 cup light brown sugar
- 2 teaspoons baking soda
- 1 cup M&Ms
- 1/2 cup semi-sweet chocolate chips
Instructions
- First, preheat the oven to 350ºF and spray a 9×13-inch baking dish with cooking spray.
- Add oats, peanut butter, maple syrup, melted butter, eggs, brown sugar, and baking soda to a large bowl and mix with a wooden spoon to combine. The batter should be thick like cookie dough.
- Then, add in M&M’s and chocolate chips. Mix again.
- Transfer dough into the baking dish and use your wooden spoon (or hands) to press the batter firmly into the dish.
- Bake at 350ºF for around 17-20 minutes or until the sides begin to turn golden brown and it is firm to touch.
- Let monster bars cool for at least 30 minutes to 1 hour before slicing and serving.
Watch It
Nutrition
Nutrition information is automatically calculated, so should only be used as an approximation.
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I’m gonna use shredded coconut unless someone stops me 👀
These bars are a crowd pleaser! So delicious!!
Such a crowd pleaser!
These monster cookie bars were better then I expected! For no flour and no granulated white sugar they have a nice consistency and are a very yummy snack. I forgot to add the butter so it was a little on the crumbly side but it still turned out great. I also added peanut m&m’s instead of regular and that was yummy. Thanks for your recipes!!
These bars are delicious! My husband who shies away from anything labeled gluten free loved them!
Everything tastes great but it turned out to be very soft and didn’t stay together. We let it sit for an hour but it’s moreso like we are eating oatmeal Vs solid bars. Any suggestions? Freezer?
My daughter in law is celiac and most of the family shies away from gluten free desserts – even though they’re still delicious – these were the favorite treats at our family reunion!
What about an egg alternative? These look heavenly!