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+ servings
cookies with REESE'S Pieces and chocolate chips
4.92 from 12 votes
Nutrition Facts
Chewy Peanut Butter Oatmeal Monster Cookies
Amount Per Serving (1 cookie)
Calories 324 Calories from Fat 156
% Daily Value*
Fat 17.3g27%
Saturated Fat 7.8g49%
Polyunsaturated Fat 1.6g
Monounsaturated Fat 2.7g
Cholesterol 35.4mg12%
Sodium 218.7mg10%
Potassium 69.3mg2%
Carbohydrates 39.5g13%
Fiber 2.7g11%
Sugar 23.2g26%
Protein 5.7g11%
Vitamin A 345IU7%
Vitamin C 0.9mg1%
Calcium 20mg2%
Iron 2.2mg12%
* Percent Daily Values are based on a 2000 calorie diet.
Servings:12 cookies
Chewy Peanut Butter Oatmeal Monster Cookies
Prep Time:
15 mins
Cook Time:
11 mins
Big, chewy peanut butter oatmeal cookies loaded with sweet chocolate chips and yummy REESE’S Pieces candies!
  • 1/2 cup butter, softened
  • 1 cup brown sugar
  • 1/2 cup creamy peanut butter
  • 1 large egg
  • 2 teaspoons vanilla extract
  • 3/4 cup all-purpose flour
  • 1 teaspoon baking soda
  • 1 teaspoon cornstarch
  • 1/4 teaspoon baking powder
  • 1/4 teaspoon salt
  • 1 1/2 cups quick oats
  • 1/2 cup mini semi-sweet chocolate chips
  • 1 cup REESE’S Pieces or M&M candies
  1. Preheat oven to 350ºF and line baking sheets with parchment paper and set aside.
  2. In a large bowl, cream together butter, brown sugar, and peanut butter with a hand or stand mixer until light and fluffy, about 3-4 minutes. Mix in the egg and vanilla, scraping down the sides of the bowl as needed.
  3. In a separate bowl, add the flour, baking soda, cornstarch, baking powder, salt, and quick oats; whisk to combine. With the mixer on low speed, slowly add the flour mixture to the wet ingredients and mix until just combined. Stir in the chocolate chips and REESE’S Pieces candies by hand.

  4. Measure out ¼ cup balls of dough and place them on the baking sheets. Bake the cookies for 11-13 minutes, until the edges are just starting to brown and the top still looks slightly undercooked. Remove from the oven and cool for 5 minutes on the baking sheet before moving them to a wire rack to cool completely. Before these have cooled completely, they will be crumbly. I suggest letting them cool completely before tasting.

  5. Store cookies covered at room temperature for up to 1 week.
Recipe Notes

As written, this recipe makes 12 very large cookies. You can certainly make 24, more normal-sized cookies.  

3-4 minutes will seem like a long time to mix the sugars, peanut butter, and butter but it's really important. The dough will become much lighter in color and look fluffy. That's when you know you have blended it long enough.

For a flatter cookie, take the bottom of a drinking glass and gently press down on the cookie right after they come out of the oven OR just press some additional candies on the tops of the cooked cookies and that will naturally press them down into more of a cookie shape, I always do this and it works so well. The cookies don't spread much at all while baking.
Natural peanut butter does not work well in this recipe. I used the original Jif.
Press some additional candy pieces and chocolate chips on top of the cookie dough balls, before putting cookie sheet in the oven, for a pretty presentation.
Freezing Instructions: Baked and cooled cookies freeze well for up to 3 months. Unbaked cookie dough balls freeze well for up to 3 months too. Bake frozen cookie dough balls for an extra minute, no need to thaw.

Author: Kim
Course: Dessert
Cuisine: American
Keyword: Easy Monster Cookies, Peanut Butter Monster Cookies, REESE’S Pieces Monster Cookies

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