These monster cookies are loaded with peanut butter, chocolate chips, oats and M&Ms. The result: soft, chewy, thick cookies full of texture and big on flavor—big enough to please both kids and adults.
This recipe was updated November 3, 2022 with new photos, tips and minor adjustments.
Monster cookies are a mash-up of oatmeal cookies, peanut butter cookies, chocolate chip cookies and M&M cookies. They bake up soft and chewy with an assertive peanut butter flavor that pairs perfectly with chocolate. This recipe makes thick cookies that can hold plenty of chips and candies while staying tender in the middle. The dough does not need chilling, although you can freeze the dough balls for later baking.
Monster Cookie Recipe
The core ingredients in these monster cookies are peanut butter, oats, chocolate chips and M&Ms. Below are clear, streamlined instructions; the ingredient list and nutrition facts follow.
- Preheat the oven to 350°F (180°C or 170°C convection). Line cookie sheets with parchment paper or silicone baking mats.
- In a large bowl, beat the softened butter with the brown sugar, granulated sugar and peanut butter until smooth. Using equal amounts of butter and peanut butter gives a great balance of richness and flavor.
- Mix in the egg and vanilla extract. Room-temperature egg yields the best texture.
- Turn off the mixer and add the flour, cornstarch, baking powder, baking soda and salt. Stir a few times by hand to avoid a flour cloud, then mix briefly on low until combined.
- Stir in the oats. Use old-fashioned (large rolled) oats for the best texture; quick oats will work in a pinch, but steel-cut or instant oats are not recommended.
- Fold in the chocolate chips and M&Ms. Use mini or regular candies depending on preference.
- Form the dough into balls. A cookie scoop keeps hands cleaner and ensures even cookies. For large cookies, make dough balls about 3 tablespoons each (I used two 1.5-tablespoon scoops to reach ~3 tablespoons).
- Place dough balls 2–3 inches apart on the lined sheets and bake one sheet at a time for 10–12 minutes, until the tops look set. Optionally press a few extra chocolate chips or M&Ms onto the warm tops for a pretty finish.
Note: If making smaller cookies (~1.5 tablespoons dough each), bake about 8–10 minutes.
Freezing the Dough
Yes—make the dough, form it into balls, place them in a freezer bag (remove excess air) and freeze up to 2 months. Bake from frozen; add 1–2 minutes to the bake time as needed.
These monster cookies combine peanut butter, chocolate and chewy oat goodness in an easy, reliable recipe. Serve with a cold glass of milk and enjoy. 
Ingredients
- 1/2 cup (112 g) unsalted butter, softened
- 1/2 cup (100 g) brown sugar
- 1/3 cup (66 g) granulated sugar
- 1/2 cup (130 g) smooth peanut butter (commercially prepared)
- 1 large egg
- 1 teaspoon vanilla extract
- 3/4 cup plus 2 tablespoons (109 g) all-purpose flour
- 1 tablespoon cornstarch
- 1/2 teaspoon baking soda
- 1/2 teaspoon baking powder
- 1/4 teaspoon salt
- 1 cup (90 g) old-fashioned rolled oats
- 1/2 cup (95 g) chocolate chips, plus more for topping
- 1/2 cup (about 100 g) M&Ms, plus more for topping
Instructions (Concise)
- Preheat oven to 350°F (180°C). Line two cookie sheets.
- Cream butter, brown sugar, granulated sugar and peanut butter until smooth.
- Beat in the egg and vanilla.
- Add flour, cornstarch, baking powder, baking soda and salt. Stir by hand then mix on low until combined.
- Fold in oats, then chocolate chips and M&Ms.
- Scoop dough into balls (~3 tablespoons each for large cookies) and place 2–3 inches apart on prepared sheets.
- Bake one sheet at a time for 11–13 minutes, until tops look set. Cool on the sheet for at least 10 minutes, then transfer to a rack. Press a few extra chips or M&Ms into the warm tops if desired.
Notes
- Peanut butter: Use smooth commercial peanut butter for consistent results—natural or oil-separated varieties change the texture.
- Oats: Old-fashioned rolled oats give the best texture. Avoid steel-cut or instant oats.
- M&Ms: Regular or mini both work well.
- Storage: Store cooled cookies in an airtight container at room temperature up to 4 days.
- Freezing: Freeze baked cookies or freeze dough balls for up to 2 months. Bake frozen dough an extra 1–2 minutes.
Recipe Details
Yield: about 16 large cookies. Prep time: 15 minutes. Cook time: 12 minutes. Total time: ~45 minutes.
Nutrition (per cookie, estimated)
Calories: 250 kcal; Carbohydrates: 29 g; Protein: 4 g; Fat: 13 g; Sugar: 19 g. Values are approximate and based on 16 equal-sized cookies.