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A stack of monster cookies on a speckled plate.

Soft and Chewy Monster Cookies

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Peanut butter oatmeal cookies packed with M&M's and chocolate chips. These monster cookies are incredibly soft, chewy, thick, and so easy to make!
Course Dessert
Cuisine American
Keyword monster cookie recipe, soft and chewy monster cookies
Prep Time 15 mins
Cook Time 12 mins
Total Time 27 mins
Servings 32 cookies
Author Danielle


  • 1 cup (125 grams) all-purpose flour , spooned & leveled
  • 1 1/4 cups (125 grams) old-fashioned rolled oats
  • 1/2 teaspoon baking soda
  • 1/4 teaspoon salt
  • 1/2 cup (115 grams) unsalted butter , softened
  • 3/4 cup (150 grams) brown sugar , lightly packed
  • 1/4 cup (50 grams) granulated sugar
  • 1/2 cup (125 grams) creamy peanut butter
  • 1 large egg , room temperature
  • 1 teaspoon pure vanilla extract
  • 3/4 cup (150 grams) M&M's
  • 1/2 cup (95 grams) semi-sweet chocolate chips


  • Preheat oven to 350°F (177°C). Line two large baking sheets with parchment paper or silicone baking mats and set aside.
  • In a large mixing bowl, whisk together the flour, old-fashioned rolled oats, baking soda, and salt. Set aside.
  • In the bowl of a stand mixer fitted with the paddle attachment, or in a large mixing bowl using a handheld mixer, cream together the butter, brown sugar, and granulated sugar for about 1-2 minutes or until well combined. Mix in the peanut butter, egg, and vanilla extract until fully combined, making sure to stop and scrape down the sides of the bowl as needed.
  • Slowly mix in the dry ingredients until just combined. Add the M&M's and chocolate chips and gently fold them into the cookie dough.
  • Using a 1.5 tablespoon cookie scoop, scoop balls of cookie dough onto the prepared baking sheets, making sure to leave a little room between each one.
  • Bake in separate batches at 350°F (177°C) for 10-12 minutes or until the tops of the cookies are set. Remove from the oven and allow to cool on the baking sheet for 5-10 minutes, then transfer to a wire rack to cool completely. 


Peanut Butter: It's best to use a no-stir creamy peanut butter like Jif or Skippy for these cookies.
Egg: To get your egg to room temperature quickly, place it in a bowl of warm water for 5-10 minutes.
Storage Instructions: Store cookies in an airtight container on the counter for up to 5 days.
Freezing Instructions: Scoop balls of the cookie dough onto a baking sheet lined with parchment paper. Freeze for several hours or until the cookie dough is completely frozen, then store in a freezer bag or container. Cookie dough balls may be baked from frozen for an additional 1-2 minutes.
Baked cookies will also freeze well for up to 3 months. Thaw to room temperature on the counter before serving.