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These Monster Cookie Bars take my most popular monster cookie recipe and turn it into an easy, no-scoop dessert you bake right in a 9x13 pan. They’re thick and chewy peanut butter oatmeal bars loaded with M&M’s and chocolate chips, with crisp golden edges and a soft, gooey center. If you love monster cookies but don’t want to scoop and bake batch after batch, these monster bars are for you. They are made in one bowl and feed a crowd.
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Monster Cookie Bars

These Monster Cookie Bars are thick, chewy peanut butter oatmeal bars loaded with M&M’s and chocolate chips. One bowl, one 9x13 pan, and no scooping! How to make the best monster cookie bars.
Prep Time15 minutes
Cook Time24 minutes
Course: Dessert
Cuisine: American
Keyword: monster cookie bars
Servings: 24
Author: Modern Honey® - www.modernhoney.com

Ingredients

  • 1 cup Unsalted Butter (softened)
  • 1 cup Brown Sugar
  • 1 cup Sugar
  • 1 cup Creamy Peanut Butter (Skippy's or Jif)
  • 2 large Eggs
  • 2 teaspoons Vanilla Extract
  • 1 1/2 cups Rolled Oats (or quick oats)
  • 2 cups Flour
  • 1 teaspoon Baking Soda
  • 1/2 teaspoon Salt
  • 2 cups Plain M&M's
  • 1 1/2 cups Chocolate Chips

Instructions

  • Preheat the oven to 350°F. Line a 9x13-inch pan with parchment paper, leaving some overhang on the sides so you can lift the bars out, and lightly spray it with nonstick spray. A light-colored metal pan works best.
  • Beat the softened butter, brown sugar, and sugar for 2 to 3 minutes, until light and fluffy.
  • Add the peanut butter, eggs, and vanilla. Mix in the peanut butter until smooth, then add the eggs one at a time and the vanilla.
  • Add the oats, flour, baking soda, and salt. Mix on low just until combined.
  • Stir in the M&M's and chocolate chips, saving about ½ cup of M&M's for the top.
  • Spread the dough evenly into the pan, pressing it all the way into the corners, and smooth the top. Press the reserved M&M's into the top so they look pretty after baking.
  • Bake for 22 to 28 minutes. Start checking at 22 minutes. They're done when the edges are golden and set, the top is lightly golden, and the center looks just barely set and slightly soft. A toothpick in the center should come out with moist crumbs, not wet batter. If the edges are browning too fast before the center is done, loosely cover the pan with foil for the last 5 to 10 minutes.
  • Cool completely. Let the bars cool in the pan for at least 1½ to 2 hours before cutting. They'll finish setting as they cool, and cutting too early makes them fall apart.
  • Cut and serve. Lift the bars out using the parchment and cut into 24 bars.

Notes

  • Don't overbake. Pull the bars when the edges are golden and the center looks just set. They firm up as they cool.
  • Peanut butter: Use a creamy, no-stir brand. Do not use natural peanut butter.
  • Gluten-free: Use certified gluten-free oats and gluten-free flour. 
  • Aluminum Pan: I suggest using a metal aluminum pan rather than a glass pan. Glass pans bake differently (harder edges and undercooked centers).
  • Cutting: Cool completely, or chill 20 minutes, for clean slices.
  • Storage: Keep airtight at room temperature up to 4 days, or freeze up to 3 months.

Nutrition

Calories: 402kcal | Carbohydrates: 53g | Protein: 8g | Fat: 19g | Saturated Fat: 7g | Polyunsaturated Fat: 3g | Monounsaturated Fat: 6g | Trans Fat: 0.1g | Cholesterol: 18mg | Sodium: 170mg | Potassium: 168mg | Fiber: 3g | Sugar: 37g | Vitamin A: 84IU | Vitamin C: 0.2mg | Calcium: 58mg | Iron: 2mg
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