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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If you’re a fan of cookies and bars, you’re in for a treat with these Monster Cookie Bars. These bars are a perfect combination of your favourite cookies and are packed with delicious, chunky, and chewy flavour that will leave your taste buds wanting more.
Can I use honey instead of maple syrup?
Definitely!
Would raisins work, instead of m&m’s ?
Definitely!
thank you for your quick reply 🙂
Thanks for the great recipe!
Hello, thanks for sharing this recipy! So amazing!
Delicious recipe! Thanks for the easy step-by-step instructions. Will definitely make again. Highly recommend!
So glad you enjoyed these monster cookie bars!
I made this recipe for myself, my husband, and my two boys (9 and 6), and we all loved it! So quick and easy!
So happy to hear you and the fam loved these monster cookie bars, Katie!
I just baked them one handed with baby in the other arm, that’s my kind of recipe!! 😅thank you so much 💕💕💕💕 so good and so easy!
Can I use chunky peanut butter in this recipe or will it affect the texture too much? I love monster cookies 🙂
It says baking soda in 2 places but never an amount. How much soda? The cookies would be very good.
Hi Marilyn! You use 2 teaspoons!