Monster Cookie Bars
Monster Cookie Bars are a chocolatey, peanut butter, oatmeal cookie in bar form and stuffed with M&Ms. If you’ve never tried Monster Cookies before, these might just be your new favorites.
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Monster Cookie Bar Recipe
I love baking cookie bars because they are a bit faster to make than regular cookies. This is because you don’t have to roll the dough into balls; you just press it straight into a baking pan and then cut the bars into your desired size after baking. This makes cookie bars great for serving to large groups.

Ingredients for Monster Cookies Bars
- Salted Butter (softened) – I always used salted butter. If you only have unsalted, just add an extra pinch of salt to the dough.
- Peanut Butter – I use creamy peanut butter for this recipe, but you could definitely use crunchy peanut butter, if you prefer. I personally haven’t tested this recipe with natural peanut butter so I’m not sure how it would affect the texture.
- Brown Sugar – Be sure to always pack your brown sugar when measuring.
- Granulated Sugar
- Egg
- Vanilla
- All Purpose Flour
- Oats – Make sure you use old fashioned rolled oats, not quick oats.
- Baking Soda
- Baking Powder
- Salt
- Semi Sweet Chocolate Chips – Feel free to use milk chocolate chips if you prefer.
- M&Ms – I like to use a mix of regular M&Ms and mini M&Ms.

How to Make Monster Cookie Bars
- Begin by lining a 9×9 pan with parchment paper, then set aside.
- Prepare the oven by preheating it 350°F.
- In the bowl of a stand mixer, or using a handheld electric mixer, cream together the butter, peanut butter, brown sugar and granulated sugar until smooth and creamy.
- Next, add the eggs and vanilla and mix until well combined.
- Then, add the flour, oats, baking soda, baking powder and salt and mix until a sticky dough forms.
- Lastly, mix in the chocolate chips and M&Ms until evenly distributed throughout the dough.
- Next, pour the dough into your prepared baking pan.
- Use clean hands to loosely press and pack the dough into the pan.
- Bake at 350°F for 25-30 minutes or until the top of the bars are golden brown.
- After baking, allow the cookie bars to cool completely before removing from the pan and cutting.
- Enjoy!
- Store your Monster Cookie Bars in an airtight container for 3-4 days at room temperature.

What are Monster Cookies made of?
Monster Cookies are a combination of many flavors – peanut butter, oats, vanilla, chocolate and (the best part), M&M’s!
Why are my Monster Cookie bars falling apart?
If your cookie bars are dry and falling apart, this usually means they were over baked. Try cooking them for a few less minutes next time.
How to store and freeze cookie bars:
Always allow your cookie bars to cool completely before storing. If you want to freeze the cookie bars, freeze the cut cookie bars in an airtight container for up to 3 months. Before eating, allow the frozen bars to come to room temperature by placing them on the counter for about an hour.

Recipes Similar to Monster Cookie Bars
- Fruity Pebbles Treats
- Chocolate Chip Cookie Bars
- Buckeye Brownie Recipe
- Lofthouse Cookie Recipe
- Cookie Dip

Monster Cookie Bars
Ingredients
- 1/2 cup salted butter softened
- 1/4 cup peanut butter
- 1 cup brown sugar
- 1/4 cup granulated sugar
- 2 eggs
- 2 tsp vanilla extract
- 2 cups all purpose flour
- 1 cup rolled oats
- 1 tsp baking soda
- 1/2 tsp baking powder
- 1/2 tsp salt
- 1 cup semi sweet chocolate chips
- 3/4 cup m&m's
Instructions
- Line a 9×9 pan with parchment paper and set aside.
- Preheat oven to 350° F
- .Cream together the butter, peanut butter, brown sugar and granulated sugar until smooth and creamy.
- Add the eggs and vanilla. Mix until well combined.
- Add the flour, oats, baking soda, baking powder and salt. Mix until a sticky dough forms.
- Lastly, mix in the chocolate chip sand m&m’s.
- Pour the mixture into the prepared pan and loosely press and pack the dough into the pan.
- Bake at 350° for 25-30 minutes or until the tops are golden brown.
- Allow the cookie bars to cool completely before removing from the pan and cutting.
- Enjoy!
- Store in an airtight container for 3-4 days at room temperature.