Chewy Monster Cookies

by Haley // September 11, 2025

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Whip up a batch of thick and chewy monster cookies packed full of oats, peanut butter and m&m candies. This quick and easy recipe has the perfect texture and flavor.

Monster cookies on a round wire cooling rack on tabletop.

When it comes to cookies, I’m all about texture and flavor. I love a good oatmeal cookie, but also can’t resist m&m cookies. So why not combine the two and throw in some peanut butter for good measure? The result is the oh-so-popular monster cookie. They earned their name from all the delicious ingredients packed inside!

Table of Contents

Why You’ll Love This Recipe

Thick and chewy texture. The oats provide a chewy texture while chilling the dough ensures an extra thick, bakery-style cookie.
Full of flavor. The peanut butter stands out and is complemented by the chocolate m&m candies.
Easy to make. The recipe has simple steps and the dough comes together in minutes.
Perfect for parties. Whether it’s a birthday or Halloween party, monster cookies are always a popular treat! Try this monster cookie bars variation next.

Ingredient Notes

tabletop with bowls of ingredients to make monster cookies.

Flour: Use all-purpose flour as the base for the dry ingredients.
Oats: Rolled oats, also known as old-fashioned oats, help create a chewy texture.
Baking soda: This leavening agent helps the cookie dough rise and spread.
Salt: Salt helps activate the baking soda and offset the sweetness.
Butter: Use unsalted butter that is room temperature. Different brands of salted butter have various amounts of salt added so it’s best to add the salt separately.
Peanut butter: No-stir creamy peanut butter is best for this recipe. I prefer Skippy All-Natural. Do not use the kind where oil sits at the top of the jar.
Sugar: Granulated sugar adds sweetness and moisture to the cookies.
Brown sugar: Light brown sugar helps create a chewy texture and adds a subtle molasses flavor.
Eggs: Use one egg and one egg yolk to help bind the ingredients.
Vanilla: 100% pure vanilla extract adds warmth and depth of flavor.
M&M candies: Classic monster cookies always have m&m’s mixed in!
Chocolate chips: Semisweet chocolate chips are used for extra chocolate flavor in each bite!

Refer to the recipe card for ingredient details and measurements.

Recipe Variations

Make giant cookies. Looking for a cookie with monstrous proportions? Scoop 3 Tablespoons of dough and roll into balls to make extra large cookies. Baking time will be 15 to 16 minutes.

Stir in some nuts. For even more flavor and texture, stir in 1/2 cup roughly chopped peanuts, almonds or walnuts to the dough.

Add a spooky touch. After rolling the dough into balls, press some eye candies into the top for a monster effect for Halloween.

How to Make Monster Cookies

photo collage demonstrating how to make monster cookie dough in a mixing bowl with a hand mixer.

Whisk together the dry ingredients: flour, oats, baking soda and salt. Set aside.
Mix the wet ingredients. Beat butter, peanut butter, sugar and brown sugar until light and fluffy. Add the egg, egg yolk and vanilla, then mix until combined.
Add the dry ingredients to the wet ingredients. Mix just until combined. Stir in the chocolate chips and M&M candies.
Cover the dough and chill for at least 2 hours.

photo collage demonstrating how to scoop, roll and bake monster cookie dough.

Preheat oven to 350 F. Line a baking sheet with parchment paper. Scoop dough and roll into balls. Place on baking sheet 1 1/2 inches apart.
Bake cookies at 350 F for 10 to 12 minutes. Cool on the pan for a few minutes before transferring to a wire rack to cool completely.

Expert Tips

Weigh the ingredients. Use a kitchen scale for accurate measurements. If you don’t have a scale, use the spoon and level method for the flour. Never pack flour down into the measuring cup.

Use room temperature ingredients. Not only are they easier to mix, but they also create a more consistent dough. As a result, the cookies will have a better texture.

Chill the dough. For the ultimate chewy texture, chill the dough for at least 2 hours or ideally overnight.

chewy monster cookies layered on top of each other.

Make Ahead and Storage Tips

Make ahead the dough and store in the refrigerator for up to 48 hours. Alternatively, you can freeze the dough for up to 3 months. Form the dough into a log, wrap in plastic wrap and store in the freezer. When ready to bake, defrost in the refrigerator before scooping and baking.

Store cookies in an airtight container at room temperature for up to 1 week.

Freeze baked cookies for up to 3 months. After they have cooled, wrap stacks of 4 or 5 cookies in plastic wrap. Store in a freezer bag or airtight container to prevent freezer burn.

Recipe FAQ

Can I use quick oats instead of regular oats?

Yes, but the texture of the cookies will be softer and less chewy. Quick oats absorb more liquid while rolled oats provide more texture.

Does crunchy peanut butter work in this recipe?

Yes, but make sure it’s the no-stir variety. Do not use peanut butter where the oil separates and sits on top.

Why are my monster cookies dry and crumbly?

Most likely too much flour was added or the cookies were over-baked. Use a kitchen scale for accurate measuring and check that your oven temperature is accurate by using an oven thermometer.