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Monster Cookie Bars

Monster Cookie Bars are a holiday favorite and these delicious chewy bars are made with old-fashioned oats, peanut butter, chocolate chips, and M&M’s.

These quick and easy-to-make bars are made with simple everyday ingredients are a fun addition to cookie tins during the holidays!

Monster cookie bars on a round wire rack.

Ingredients in Monster Cookie Bars

Unsliced 9x9 monster cookie bars resting on a wire rack.

RELATED: Monster Cookies

How to Make Monster Cookie Bars

Preheat the oven and prepare the baking dish – Preheat the oven to 350°F and line a 9×9 baking dish with parchment paper and lightly grease the sides of the pan.

TIP: Allow the parchment paper to overhang on two sides so that once the monster cookie bars are done it is easy to lift the bars out of the dish without sticking.

Blend the wet ingredients- Using a hand mixer or stand mixer cream together the butter, granulated sugar, and brown sugar. Add in the egg and vanilla, and blend until well combined. Next, the peanut butter is beat into the mix until the mixture is smooth.

Mix the dry ingredients- Combine the flour and the baking soda together and then mix it into the peanut butter mixture. Blend in the old-fashioned oats and stir until the oats are moistened.

Add the mix-ins- Stir in M&M’s and the chocolate chips until the mix-ins are mixed into the dough.

Monster cookie bars cut into squares with white linen background.

RELATED: Chocolate Chip Cookie Bars

Transfer the dough to the baking dish- Evenly spread the mixture into the prepared 9×9 baking dish. Sprinkle the top with additional M&M’s and chocolate chips then gently press them down into the top of the dough.

Bake the monster cookie bars – Bake for 18-20 minutes. The outer parts of the dish should be lightly brown but the center will not quite be done. The bars will continue to bake while cooling in the pan.

Allow the dish to cool before slicing-Allow to cool completely before cutting into squares and removing it from the pan to prevent crumbling. This will allow the bars to “set” so they will be tender and chewy.

Sliced Monster Cookie Bars on cooling rack.

Gluten Free Monster Cookies

This recipe has flour in it so it’s not gluten-free. However, my recipe for Monster Cookies is gluten-free and can even be made nut-free! The monster cookies version is a family tradition that I made as a child with my mother and I now make with my kids! If you’re looking for a peanut butter alternative, Wowbutter is a great option and it provides the same creaminess and delicious flavor as peanut butter in this recipe.

Yield: 9 bars

Monster Cookie Bars

Monster cookie bars with some stacked in the background on black wire rack.

Monster Cookie Bars are a holiday favorite and these delicious chewy bars are made with old-fashioned oats, peanut butter, chocolate chips, and M&M’s.

Prep Time 10 minutes
Cook Time 18 minutes
Total Time 28 minutes

Ingredients

  • 1/2 cup butter softened
  • 3/4 cup brown sugar packed
  • 1/2 cup granulated sugar
  • 1 egg
  • 1/2 teaspoon salt
  • 1 teaspoon vanilla extract
  • 1 cup creamy peanut butter
  • ½ cup all purpose flour
  • 1/2 teaspoon baking soda
  • 1 3/4 cups old fashioned oats
  • 1 cup semisweet chocolate chips
  • 1 cup M&Ms

Instructions

    1. Preheat the oven to 350.
    2. Line a 9x9 baking dish with parchment paper and lightly grease the sides.
    3. Using a hand mixer or stand mixer on medium speed, cream together butter and both sugars.
    4. Add in the egg and vanilla, mixing well.
    5. Mix in peanut butter until smooth.
    6. Combine the flour and the baking soda together and then mix it into the peanut butter mixture.
    7. Blend in the old fashioned oats.
    8. Stir in M&M’s and the chocolate chips.
    9. Evenly spread mixture into the 9x9 baking dish.
    10. Sprinkle the top with M&M’s and additional chocolate chips then gently press them down into the top of dough.
    11. Bake for 18-20 minutes. The outer parts of the dish should be lightly brown.
    12. Allow to cool completely before cutting into squares and removing from the pan to prevent crumbling.
    13. Store in an airtight container.

Notes

The bars must cool completely before removing them from the pan because they will crumble and fall apart. Allowing them to cool will help them keep their shape.

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Nutrition Information:

Yield:

9

Serving Size:

1

Amount Per Serving: Calories: 661Total Fat: 37gSaturated Fat: 16gTrans Fat: 0gUnsaturated Fat: 17gCholesterol: 51mgSodium: 435mgCarbohydrates: 78gFiber: 5gSugar: 53gProtein: 12g

Nutrition calculation is a rough estimate and can vary depending on the cooking technique and the exact ingredients used. For informational purposes only.

Did you make this recipe?

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Padmajha V

Saturday 6th of November 2021

This is such a a fun idea and the kids will love to have somehting so colorful and full of candy!

Gail Montero

Wednesday 3rd of November 2021

Wow! This looks loaded with deliciousness for sure. Need to add this to my holiday list!

Natalie

Wednesday 3rd of November 2021

These cookie bars look fantastic. Such a perfect family treat. I have some candy leftovers from Halloween. I'm going to bake these bars for the weekend.

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