Marshmallow Monster Cookies are my soft batch monster cookies filled with marshmallow fluff for a supersized cookie that is irresistible! When I say supersized, I mean it! I could only fit 2-3 cookies on each baking sheet! After trying this method with my Marshmallow Chocolate Chip Cookies (which you will have to try, too), I knew I had to give it a whirl with monster cookies! And yes, it worked!

Marshmallow Monster Cookies in a pan on a white table from overhead.
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Ingredients & Substitutions

Butter: I like using unsalted butter to have the most control over salt added to recipes. If using salted butter, you may want to lessen the amount of salt in the cookie dough.

Peanut Butter: Although I used creamy peanut butter, you could substitute crunchy for more texture. Or, try the cookies with almond butter or other nut butter.

Brown Sugar: Light brown sugar sweetens the cookies and contributes to their chewiness and softness. You can substitute with an equal amount of granulated sugar or dark brown sugar for a slightly different flavor.

Oats: For the most texture, I use old-fashionedd oats, also called rolled oats, in the recipe. If you only have quick oats, you could use those in a pinch.

Adding M&M’s and Chocolate Chips: When adding solid ingredients (like these candy-coated chocolates and chips), I prefer to stir them in by hand. If you are using your mixer, mix them in on low for only about 5 seconds. I like to have some mini M&M’s on hand for the topping, but those are optional.

Marshmallow Fluff: Adding marshmallow fluff to these cookies gives you ooey-gooey delicious bites each time! Marshmallow fluff, also called marshmallow creme, is a sticky concoction with a marshmallow taste. Make your own if you don’t have any on hand!

Close up of Marshmallow Monster Cookie.

Can I Use Regular Marshmallows Instead Of Marshmallow Fluff?

No, I do not recommend using regular marshmallows in place of the marshmallow fluff. When we tested our marshmallow chocolate chip cookies with regular marshmallows, it did not work. The marshmallows just kind of dissolved when baked. Then, you miss out on that ooey-gooeyness you want!

Assembling Marshmallow Monster Cookies Ahead Of Time

If you want to get a head start on these cookies, get them assembled up to a day in advance. Once the cookies are filled with marshmallow fluff and sealed, place them onto a baking sheet lined with parchment paper. Cover the baking sheet with plastic wrap or aluminum foil to prevent the cookies from drying out. Then, refrigerate for a few hours or overnight before baking. When ready to bake the cookies, let them sit at room temperature for about 10-15 minutes before baking to slightly soften the dough and ensure even baking.

Marshmallow Monster Cookies on a white table with center cookie broken in half showing gooey marshmallow.

Can I Make The Cookies Smaller?

Yes, since these cookies bake up large, you can just use less cookie dough for each disc of dough. You will end up with more cookies, and the baking time may need to be adjusted.

Stack of Marshmallow Monster Cookies with top cookie broken in half showing inside texture.

How To Store Marshmallow Monster Cookies

To keep your Marshmallow Monster Cookies fresh and tasty, follow these simple steps:

  1. Allow the cookies to cool completely after baking. This ensures they retain their delightful texture and flavor.
  2. Store them in an airtight container at room temperature. If you’re stacking the cookies, place parchment paper between layers to prevent sticking.
  3. Enjoy your cookies within 2-3 days for the best taste and texture.
  4. If you want to save some for later, you can freeze the cookies in a freezer-safe container for up to 2-3 months. Just be sure to let them thaw at room temperature before indulging in their deliciousness!

Check out my Guide to Freezing, Baking, and Storing Cookies for more helpful tips.

Marshmallow Monster Cookies in a pan on a white table from overhead.

Marshmallow Monster Cookies

Prep Time 20 minutes
Cook Time 15 minutes
Total Time 35 minutes
These Marshmallow Monster Cookies boast a soft, chewy texture surrounding a gooey marshmallow fluff center. Bursting with vibrant M&M candies and chocolate chips, they're the perfect solution for your sweet tooth cravings!


  • 1 cup (2 sticks / 227 g) unsalted butter, room temperature
  • 1 cup (258 g) creamy peanut butter
  • 1 ½ cups (300 g) light brown sugar, packed
  • 2 large eggs, room temperature
  • 2 cups (250 g) all-purpose flour
  • 1 cup (90 g) old-fashioned oats
  • 1 teaspoon baking soda
  • ½ teaspoon kosher salt
  • 1 ½ cups plain M&M candies
  • 1 ½ cups (252 g) semi-sweet chocolate chips
  • 1 jar (7 ounces) marshmallow fluff
  • mini M&M candies, for topping (optional)


  • Preheat the oven to 350°F. Line baking sheets with parchment paper. Set aside.
  • In the bowl of a stand mixer with a paddle attachment (or a handheld mixer), beat the butter on medium-high speed until smooth (about a minute).
  • Add the peanut butter. Beat for about 2 minutes, or until smooth.
  • Add brown sugar. Mix on medium-high speed until smooth (about 2 minutes).
  • Add eggs, one at a time, mixing for 30 seconds after each addition. Scrape down the sides of the bowl and beat ingredients together again, if necessary.
  • With the mixer off, add the flour, oats, baking soda, and salt. Mix on low until just combined, being careful not to overmix.
  • With the mixer still on low (or by hand), add the M&M’s and chocolate chips and mix until incorporated. (If using an electric mixer, only mix for a few seconds.)
  • Using a 2-tablespoon cookie scoop, drop dough onto the lined baking sheets. Using your hand, flatten each dough ball into a flat disk shape. You should have about 38 cookie dough disks.
  • Using two spoons (this will keep your hands from getting sticky), add about 1 tablespoon of marshmallow fluff to the center of a disk of dough. (You can also add the fluff to a piping bag and pipe dollops onto the dough disk.)
  • Place a second dough circle on top of the fluff. Press around the outer edges to firmly seal the disks together. Repeat with the remaining dough disks and fluff. (I had a total of 19 stuffed cookies.)
  • Top each cookie with mini M&M's (optional).
  • Place 2-3 stuffed cookies onto a lined baking sheet, leaving about 4 inches of space between each cookie. These cookies are large.
  • Bake for 15-16 minutes, or until the edges are golden brown.
  • Let the cookies cool completely on the baking sheets before serving.

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What the Test Kitchen had to say about this recipe:


These marshmallow monster cookies were awesome! The combination of peanut butter, chocolate chips, and marshmallow fluff was heavenly. Plus, the mini M&M candies on top added a fun touch.


I could not wait to try these monster cookies with the marshmallow fluff, especially since I loved our marshmallow chocolate chip cookies. They did not disappoint! I love monster cookies anyway, so with the added ooey-gooey filling, they were amazing!


The marshmallow fluff in the middle of these cookies made them extra gooey and delicious. Loved the combination of peanut butter, chocolate chips, and M&M candies.


Absolutely loved the marshmallow monster cookies! The marshmallow fluff in the middle added a wonderful gooeyness, and the combination of peanut butter, chocolate chips, and M&M candies was divine.


The marshmallow monster cookies were a hit! The marshmallow fluff in the center was a delightful surprise, and the combination of flavors and textures was perfect. A definite crowd-pleaser!

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Meet Amanda Rettke

Amanda Rettke is the creator of I Am Baker, and the bestselling author of Surprise Inside Cakes: Amazing Cakes for Every Occasion – With a Little Something Extra Inside.Over the course of her 15+ year blogging adventure, she has been featured in and collaborated with the Food Network, New York Times, LA Times, Country Living Magazine, People Magazine, Epicurious, Brides, Romantic Homes, life:beautiful, Publishers Weekly, The Daily Mail, Star Tribune, The Globe and Mail, DailyCandy, YumSugar, The Knot, The Kitchn, and Parade, to name a few.

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