Go Back
monster cookie bars

Easy Monster Cookie Bars

Everyone's favorite cookie baked into bars instead!
Prep Time 15 mins
Cook Time 30 mins
Total Time 45 mins
Course Dessert
Cuisine American
Servings 16 bars


  • 1 cup creamy peanut butter
  • ½ cup unsalted butter, at room temperature
  • 1 cup lightly packed light brown sugar
  • ½ cup granulated white sugar
  • 2 large eggs
  • 1 large egg yolk
  • teaspoons vanilla extract
  • cups old-fashioned rolled oats
  • 1 cup all purpose flour
  • ½ teaspoon baking soda
  • ½ teaspoon salt
  • ½ cup semi sweet chocolate chips
  • ½ cup M&M's candy (more to sprinkle on top)


  • Preheat the oven to 350 degrees F. Generously grease a 9x9-inch pan with nonstick spray.
  • Use a handheld electric mixer to cream together peanut butter and butter in a large bowl. Beat in the brown sugar, granulated sugar, eggs, egg yolk, and vanilla extract.
  • Add the oats, flour, baking soda, and salt, and stir to combine. Stir in the chocolate chips and M&M's candy.
  • Transfer the dough to the prepared pan and spread it out evenly. Sprinkle a few more M&M’s on top.
  • Bake until the bars are golden, puffed and set- about 30 minutes. They will be more set on the outside than the inside, and will set more as they cool. Like brownies, be careful not to over-bake.
  • Cool slightly before cutting and serving.
Keyword cookie bars, cookies, monster