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Monster Cookie Bars are soft and chewy peanut butter-oat bars loaded with M&M’s, peanut butter chips, and chocolate chips. These thick and delicious cookie bars are perfect for sharing and totally addictive!
Want more cookie bars? Try my Chocolate Chip Cookie Bars!
Why I Love This Recipe
- Cookie Bar Perfection – These bars are perfectly soft and chewy without being too gooey in the middle or too crunchy along the edges.
- Loaded With Goodness – This version boasts not one, not two, but THREE different types of candy confections: M&Ms, chocolate chips, and peanut butter chips!
- Great For A Crowd – This batter comes together really quickly and it makes a ton of bars. This recipe is perfect when you need a large quantity of treats in one easy batch.
RECIPE WALK-THROUGH
How To Make Monster Cookie Bars
See the recipe card below for full, detailed instructions
Mix the eggs and sugars, then beat in salt, vanilla, peanut butter, butter, baking soda, and oats in a large bowl.
Add the M&Ms, chocolate chips, and peanut butter chips, mixing until just combined.
Spread the batter into the prepared baking pan. Bake for 18 to 22 minutes or until edges are very light golden brown and center is set.
Allow to cool in the baking pan before slicing and serving.
Recipe Tips
- Make Holiday Versions – You could use Reese’s Pieces in place of M&Ms for fall colors, or buy seasonal M&Ms in color schemes from Halloween to Christmas to Easter to the 4th of July for festive, holiday-themed cookie munching all year long.
- Line The Pan – I like to line the pan with parchment paper because then I can easily remove the bars to slice on a cutting board so I’m not cutting up my pan.
- Different Nut Butters – These would also be fantastic with almond or cashew butter in place of peanut butter. Try sunflower seed butter for a nut-free treat!
- Gluten-Free – This recipe is flourless, so it’s pretty easy to modify it to be gluten-free. Just use gluten-free oats and make sure any add-ins you choose are also gluten-free.
Storage Tips
The Best Way to Store Monster Cookie Bars
Store the bars in an airtight container or resealable plastic bag for 4-5 days. You can also freeze them in a freezer-safe, airtight container for up to 6 months.
More Cookie Recipes
- Cowboy Cookies
- Snickerdoodle Cookies
- Nutella Cookies
- Oreo Stuffed Cookies
- 3 Ingredient Peanut Butter Cookies
Monster Cookie Bars
Ingredients
- 4 Eggs
- 1 1/2 cups Sugar
- 1 cup Brown sugar
- 3/4 teaspoon Salt
- 1 tablespoon Pure vanilla extract
- 16 ounces Peanut butter (creamy or crunchy) 2 cups
- 5 tablespoons Butter at room temperature
- 2 1/2 teaspoons Baking soda
- 18 ounces Old-fashioned oats 5 cups
- 1 cup M&Ms
- 1/2 cup Semisweet chocolate chips
- 1/2 cup Peanut butter chips
Instructions
- Position rack in center of oven and preheat to 350°F. Generously butter a 12x18x1-inch rimmed baking sheet. Set aside.
- In a very large bowl (using a spoon or electric mixer), mix together the eggs and sugars until well-combined. Beat in the salt, vanilla, peanut butter, and butter until smooth. Stir in the baking soda (make sure there aren’t any lumps) and the oats, then add the M&Ms, chocolate chips, and peanut butter chips and mix until just combined.
- Spread the batter into the prepared baking pan, pressing down and smoothing the top into an even layer. Bake for 18 to 22 minutes or until edges are very light golden brown and center is set. Allow to cool in the baking pan before slicing and serving.
Notes
Nutrition
Nutritional Disclaimer Kristin Maxwell of “Yellow Bliss Road” is not a dietician or nutritionist, and any nutritional information shared is an estimate. For accurate calorie counts and other nutritional values, we recommend running the ingredients through your preferred online nutritional calculator. Calories and other nutritional values can vary depending on which brands were used.
oh one thing i forgot to mention is that the second batch took a lot longer to bake and i dont know why, if you know let me know.=)
this is my first time making these and i love them! its more of a fluffy cookie, but still really really good. the only reason i rated 4 starts is because i kinda wish there is more of a cream cheese flavour, but again, my first time making these and that can also be changed.thank you so much kristin!
You are so welcome sophie! Awesome feedback, thanks for stopping by.
This is by far my favorite recipe and my family loves them also <3
Nice! Thanks for stopping by Julie.