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+ servings
three monster cookie bars stacked
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5 from 2 votes

Monster Cookie Bars

These Monster Cookie Bars are thick, chewy, ultra ooey-gooey, and packed with peanut butter, oats, M&Ms, and three types of chocolate!
Prep Time15 mins
Cook Time30 mins
Total Time45 mins
Course: Dessert
Cuisine: American
Keyword: easy, m&ms, old fashioned oats
Servings: 24 bars
Calories: 333kcal
Author: Jennifer Debth

Ingredients

  • 1/2 cup unsalted butter melted
  • 1 cup dark brown sugar packed
  • 1 cup granulated sugar
  • 2 cups creamy peanut butter
  • 3 large eggs
  • 1 tablespoon vanilla extract
  • 4 cups old fashioned oats certified gluten free if necessary
  • 2 teaspoons baking soda
  • 1 teaspoon salt
  • 1 cup M&M’s plus more for topping
  • 1 cup additional mix-ins plus more for topping (I used equal parts butterscotch chips, chocolate chunks, chocolate chips, and white chocolate chips)

Instructions

  • Preheat oven to 350 degrees F and grease a 9x13 inch baking dish with cooking spray, then line it with a parchment paper sling.
  • In the bowl of your stand mixer, beat together melted butter, brown sugar, and granulated sugar until fluffy.
  • Beat in peanut butter, eggs, and vanilla until combined.
  • Add in oats, baking soda, and salt, then beat again until incorporated.
  • Beat in M&Ms and additional mix-ins (butterscotch chips, chocolate chunks/chips, white chocolate chips, etc.).
  • Pour into prepared pan, then use your hands to press the mixture into an even layer.
  • Press in extra toppings, if desired (this makes it look pretty).
  • Bake in preheated oven for 30-40 minutes or until an inserted toothpick comes out basically clean.
  • Cool completely before removing from the pan, slicing, and serving!
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Nutrition

Serving: 1bar | Calories: 333kcal | Carbohydrates: 37g | Protein: 8g | Fat: 18g | Saturated Fat: 6g | Trans Fat: 1g | Cholesterol: 35mg | Sodium: 306mg | Potassium: 211mg | Fiber: 3g | Sugar: 25g | Vitamin A: 171IU | Vitamin C: 1mg | Calcium: 39mg | Iron: 1mg