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A tray of cookie bars topped with colorful candy-coated chocolates, cut into squares, sits on parchment paper on a wooden surface. A large knife with crumbs is placed next to the tray.
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Monster Cookie Bars Recipe

The Best Monster Cookie Bars Recipe combines creamy peanut butter with oats, chocolate chips, and M&Ms on one sheet pan.
Prep Time15 minutes
Cook Time22 minutes
Total Time37 minutes
Servings: 32 Bars
Calories: 180kcal
Author: Melissa Griffiths

Ingredients 

  • ¾ cup granulated sugar
  • ⅓ cup brown sugar, packed
  • ¼ cup butter, softened
  • 1 cup creamy peanut butter
  • 1 large egg
  • 2 teaspoons vanilla extract
  • 1 teaspoon baking soda
  • ½ teaspoon salt
  • 3 cups old-fashioned oats
  • 1 cup M&M candies
  • 1 cup chocolate chips

Instructions

  • Preheat the oven to 350°F (175°C). Grease a 9x13-inch baking dish and set aside. You can also line the baking dish with parchment paper if you'd like to remove the bars for serving.
  • In a large bowl, beat together the granulated sugar, brown sugar, softened butter, and peanut butter until smooth and creamy. Add the egg and vanilla, and mix until well combined.
  • Stir in the baking soda and salt, then mix in the oats until evenly distributed. Fold in the M&M’s and chocolate chips. I like to leave ⅓ of the M&M's out of the batter and save them to press on top.
  • Press the dough firmly and evenly into the prepared baking dish. Sprinkle on extra M&M's if you saved them, and press them in firmly into the top.
  • Bake for 22–26 minutes, or until the edges are golden brown and the center is set.
  • Let cool in pan before slicing into bars.

Notes

These are naturally gluten-free; just be sure to use certified gluten-free oats.

Nutrition

Serving: 1Serving | Calories: 180kcal | Carbohydrates: 22g | Protein: 3g | Fat: 9g | Saturated Fat: 4g | Polyunsaturated Fat: 1g | Monounsaturated Fat: 3g | Trans Fat: 0.1g | Cholesterol: 11mg | Sodium: 124mg | Potassium: 95mg | Fiber: 1g | Sugar: 15g | Vitamin A: 67IU | Vitamin C: 0.04mg | Calcium: 23mg | Iron: 1mg