Have you been searching for the best easy monster cookie recipe? This is it! One-bowl peanut butter monster cookies made with oatmeal, peanut butter, and M&Ms are so much fun to make and eat. 

5 peanut butter monster cookies with oatmeal and M&Ms on a cooling rack with a bowl of m&ms on the side.

My daughter has been asking to make monster cookies ever since she saw them on Crumbl Cookie’s social media. We love baking cookies but it’s hard to choose a favorite.

While these Vegan Chocolate Chunk Cookies are one of my favorites, we also love peanut butter cookies. And cookies with oatmeal are always great too – try our Vegan Oatmeal Raisin or Cowboy Cookies if you agree. For a healthier option with similar flavors try these Trail Mix Energy Balls


What are monster cookies? These soft and chewy cookies are a combination of chocolate chip, peanut butter, and oatmeal cookies. And they always include M&Ms. 

It’s thought that monster cookies got their name from being a wild mix of flavors, a bit like Frankenstein. We think this is the best monster cookie recipe as it’s so easy to make all in one bowl. 


The ingredients for an easy monster cookie recipe made with peanut butter, oatmeal, m&m's, butter, flour, egg, and chocolate chips on a marble background.

  • Butter: Use good salted butter for the most flavorful cookies. I like to use Earth Balance baking sticks as a dairy-free vegan option. If you only have unsalted butter, be sure to add 1/4 teaspoon salt with the dry ingredients. 
  • Peanut butter: Be sure to use unsweetened peanut butter in this recipe. 
  • Light brown sugar: This ingredient adds sweetness and moisture and creates a chewy cookie. Feel free to use dark brown sugar in a pinch. 
  • Granulated sugar
  • Egg: Make sure to use room-temperature eggs when baking and use a large egg here. This ingredient helps bind the cookies together. Feel free to use a vegan egg replacer such as Bob’s Red Mill if you’re vegan. 
  • Vanilla: A favorite baking flavor, vanilla extract is essential to almost all cookie recipes. 
  • Flour: All-purpose flour creates classic chocolate chip and monster cookies. For gluten-free flourless monster cookies, use a 1-to-1 gluten-free baking flour. One of my favorite ways to make naturally gluten-free oatmeal cookies is to use gluten-free oat flour and I suspect that would work well here, though I have not tested it. 
  • Oats: Use old-fashioned rolled oats here for a hearty texture. 
  • Baking soda & powder: These are leavening agents. We have also tested this recipe with only baking powder and only baking soda and that works if you’re out of one or the other. Use 1/2 tsp baking soda or 1 teaspoon baking powder if only using one. 
  • Chocolate chips: Though I usually recommend chopped chocolate for cookies, mini chocolate chips work best here so that they don’t overpower the candies. 
  • M&Ms: Colorful candies are just a delight to add to cookie dough. You can use classic M&Ms, Reece’s Pieces, or any other candy-coated chocolate. 

Monster cookie dough with oatmeal and peanut butter is mixed together with a rubber spatula in a glass bowl.


Please find the full printable instructions at the end of this post. Here are the instructions for how to make easy one-bowl monster cookies at a glance. 

Though you can use an electric mixer for this recipe, it’s easy to make all in one bowl. To make one-bowl cookies, you’ll need to have all your ingredients at room temperature, especially the butter and peanut butter. 

Step 1: Cream together the butter, peanut butter, and sugars until fluffy. 

Step 2: Beat in the egg and vanilla. 

Step 3: Stir in the dry ingredients until well combined. 

Step 4: Bake! 

6 scoops of monster cookie dough on a parchment lined cookie sheet.


  • For Halloween Monster Cookies, add candy eyeballs. 
  • If you prefer your monster cookies less sweet, press just a few M&Ms into the cookie dough balls before baking rather than stirring in the whole amount. You can also skip the chocolate chips. 
  • You can add even more mix-ins if you’d like. Shredded coconut, roasted peanuts, peanut butter chips, and raisins are all good options. 
  • Homemade cookies last for about 4 days in an airtight container at room temperature. 


A close-up photo of a few monster cookies cooling on a rack.


Yield: about 15 cookies

Monster Cookies

Prep Time 10 minutes
Cook Time 10 minutes
Total Time 20 minutes

Monster cookies are like a cross between chocolate chip, peanut butter, and oatmeal cookies - topped off with M&Ms! These are the best soft and chewy monster cookies that are so easy to make and come together in one bowl.

A close up look at monster cookies made with m&ms, oatmeal, and peanut butter.


  • 1/2 cup butter, softened*
  • 1/2 cup peanut butter
  • 1/2 cup granulated sugar
  • 1/2 cup packed light brown sugar
  • 1 egg
  • 2 teaspoons vanilla extract
  • 3/4 cup all-purpose flour
  • 1 1/4 cups rolled oats
  • 1/2 teaspoon baking soda
  • 1/2 teaspoon baking powder
  • 1/2 cup mini chocolate chips
  • 3/4 cup M&Ms


  1. Preheat the oven to 350°F and line a baking sheet with parchment paper.
  2. In a large mixing bowl, add the butter, peanut butter, and both sugars. Cream until light and fluffy. Butter, light brown sugar, white sugar, and peanut butter in a glass bowl to begin making easy one bowl monster cookies.
  3. Add the egg and vanilla extract and continue to whisk. Egg and vanilla are added to a bowl of monster cookie dough.
  4. Add all the flour, oats, baking soda, and baking powder and stir together with a rubber spatula or wooden spoon until well combined. Stir in the M&Ms and chocolate chips. Alternatively, you can press the M&Ms into the top of the dough balls. Flour, chocolate chips, and m&ms are added to monster cookie dough in a glass bowl with a rubber spatula.
  5. Use a cookie scoop to scoop about 2 tbsp of cookie batter onto the baking sheet. Create about 15 balls, making sure there is enough space between each cookie. You might need to use two baking sheets. Balls of monster cookie dough on a parchment lined cookie sheet.
  6. Bake the cookies for 10-12 minutes or until golden brown. Allow the cookies to cool for a few minutes before serving. Homemade easy monster cookies on a cooling rack.


Monster cookies last for about 4 days at room temperature in an airtight container.

*Please use salted butter for the best flavor. If using unsalted butter, add 1/4 teaspoon with the dry ingredients.

You can use any candy-coated chocolate candies. There are gluten-free and vegan options available. Reeces Pieces are tasty if you want extra peanut butter flavor.

Vegan Monster Cookies

Use Earth Balance vegan butter sticks for baking and Bob's Red Mill Egg Replacer. Use vegan chocolates.

Gluten-Free Monster Cookies

Use certified gluten-free oats, a 1-1 gluten-free flour, and certified GF chocolates.

Nutrition Information:
Yield: 15 Serving Size: 1 cookie
Amount Per Serving: Calories: 306Total Fat: 16gSaturated Fat: 8gTrans Fat: 0gUnsaturated Fat: 7gCholesterol: 31mgSodium: 138mgCarbohydrates: 37gFiber: 2gSugar: 25gProtein: 5g

Nutrition information is automatically calculated by Nutritionix. I am not a nutritionist and cannot guarantee accuracy. If your health depends on nutrition information, please calculate again with your favorite calculator.