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4.73 from 11 votes

Thick & Chewy Monster Cookies

These Thick & Chewy Monster Cookies are one of my favorites! Huge, soft and buttery, they're fully loaded with peanut butter, chocolate chips, oats and mini M&M's for a wonderful blend of great texture and flavor!
Prep Time1 hr 10 mins
Cook Time14 mins
Total Time1 hr 24 mins
Course: Cookies, Dessert
Cuisine: American, Dessert
Servings: 12 -13
Author: Hayley Parker, The Domestic Rebel


  • 1/2 cup (1 stick) butter softened
  • 1/2 cup creamy peanut butter
  • 3/4 cup brown sugar
  • 1/4 cup white sugar
  • 2 eggs
  • 1 Tbsp vanilla extract
  • 1 tsp baking soda
  • 2 tsp cornstarch
  • cups all-purpose flour
  • 1 cup old-fashioned oats
  • 1 cup miniature M&M's candies
  • 1 cup semi-sweet or dark chocolate chips


  • In the bowl of a stand mixer, cream together the butter and peanut butter until smooth. Add in the brown sugar & sugar, creaming together until combined. Add in the eggs and vanilla, beating well. Then add in the baking soda, cornstarch and flour, mixing until combined. Mix in the oats, M&M's and chocolate chips last until just combined.
  • Cover and refrigerate dough for at LEAST 1 hour, up to overnight.
  • Preheat oven to 350 degrees F. Line 2 baking sheets with parchment or silicone liners, or spray lightly with cooking spray. Drop heaping 1/4 cup-sized balls of dough onto the baking sheets, about 2-3" apart. Bake for approx. 12-14 minutes, rotating pans halfway through baking time to ensure even cooking. Cookies may appear slightly undone in the center; this is normal and they'll continue to set as they cool. Cool on the racks. Serve warm or at room temperature.