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Chewy and chunky Kitchen-Sink Monster Cookies loaded with M&Ms and chocolate chips on a baking sheet.

Kitchen-Sink Monster Cookies

Load peanut-butter oatmeal cookies with M&Ms and chocolate chips for the ultimate treat. These Monster cookies are irresistible!
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Prep Time 15 minutes
Cook Time 9 minutes
Total Time 25 minutes
Course Dessert
Cuisine American
Servings 24
Calories 369 kcal

Ingredients
  

  • 1 cup 226g unsalted butter, softened
  • 1 cup 200g granulated sugar
  • 1 cup 220g packed brown sugar
  • 2 large eggs
  • 2 tsp 10ml vanilla extract
  • 1 cup 256g creamy peanut butter
  • 2 cups 240g all-purpose flour
  • 1 tsp 4g baking soda
  • ½ tsp 3g salt
  • 3 cups 240g rolled oats
  • 1 cup 170g M&Ms
  • 1 cup 170g semi-sweet chocolate chips
  • Optional: 1 cup mix-ins nuts, pretzels, candies

Instructions
 

  • Preheat oven to 350°F (175°C). Line baking sheets.
  • Cream butter, granulated sugar, and brown sugar until light and fluffy (3–5 min).
  • Add eggs one at a time, then vanilla and peanut butter.
  • Whisk flour, baking soda, and salt in a separate bowl.
  • Gradually mix dry ingredients into wet ingredients.
  • Stir in oats, M&Ms, chocolate chips, and optional mix-ins.
  • Drop rounded tablespoons onto baking sheets, 2 inches apart.
  • Bake 10–12 minutes until edges are golden and centers slightly soft.
  • Cool on sheets, then transfer to wire rack.
  • Enjoy warm!

Notes

Use old-fashioned oats for best texture. Avoid instant oats.