Flourless Monster Cookies: Chewy Peanut Butter Oatmeal Cookies

These flourless monster cookies are packed with peanut butter, oats, M&M’s, and chocolate chips, with crisp edges and soft, chewy centers. An easy one-bowl monster cookie recipe that’s naturally gluten free and easy to dress up for Halloween, Christmas, or any season!

Monster cookies have always felt appropriately named to me. They’re not  spooky, exactly, but because they’re loaded with just about everything you could want in a cookie. Peanut butter, oats, chocolate chips, candy pieces. A little unruly, I can vouch for the fact that, with their gooey centers. They’re hard to stop eating, especially if a tall glass of cold milk is involved.

So Why Are They Called Monster Cookies? 

As far as the cookie is concerned, the “monster” is really the sheer amount of good stuff packed inside. They’re big, loaded, and happily excessive.

In other words: the monster is mostly abundance. I can get behind that.

For Halloween, I leaned into the name with October appropriate candies, but this is really an all-year monster cookie recipe. These are flourless, wonderfully chewy through the middle, crisp around the edges, and sturdy enough to hold all that candy without falling apart.

Here are the ingredients you’ll need to make these Flourless Monster Cookies:

Eggs help bind the dough and give the cookies structure.

Creamy peanut butter provides richness, flavor, and structure. Use Jif or Skippy rather than natural peanut butter.

Light brown sugar adds moisture and keeps the centers soft and chewy.

Granulated sugar helps the edges bake up lightly crisp.

Vanilla extract rounds out the peanut butter and chocolate flavors.

Old-fashioned rolled oats give the cookies their signature hearty chew. Use certified gluten-free oats if needed.

Baking soda adds a little lift and helps the cookies spread.

Kosher salt balances the sweetness and sharpens the peanut butter flavor.

Mini semisweet chocolate chips add chocolate in every bite without overpowering the dough.

Peanut butter candies Reese’s Pieces add crunch, color, and extra peanut butter flavor. M&M’s work too.

Flaky sea salt optional, but excellent for balancing all that sweetness.

Start by whisking the eggs until they’re well combined and just a little frothy.

Add the creamy peanut butter, brown sugar, granulated sugar, and vanilla. Whisk as long as your whisk will allow, then switch to a sturdy spatula and stir until the mixture is thick, smooth, and glossy.

Add the rolled oats, baking soda, and salt. Stir until everything is evenly combined and the oats are well coated in that peanut buttery goodness.

Fold in the mini chocolate chips and Reese’s Pieces. This is where the dough officially earns its monster cookie status: a little bit of everything, preferably in every bite.

Chill the dough for about 20 minutes. This short rest gives the oats time to absorb some moisture and helps the cookies bake up thick, with crisp edges and wonderfully chewy centers.

Scoop the dough into generous two-tablespoon portions and arrange them on parchment-lined baking sheets. Press a few extra candies and chocolate chips into the tops because we eat with our eyes first.

Bake until the edges are set but the centers still look slightly soft, about 10 to 12 minutes. Don’t wait for them to look completely baked, I promise that the cookies will continue to set on the pan, and pulling them at just the right moment is the secret to that chewy middle.

Finish the warm cookies with a pinch of flaky sea salt and let them cool on the baking sheet for at least 10 minutes. They’ll go from very soft to thick, chewy, peanut buttery perfection as they cool.

Monster Cookies for Every Season

The dough stays the same; just swap the candy colors to match the moment.

• Halloween: Orange, purple, and black candies.
• Christmas: Red and green M&M’s or Reese’s Pieces.
• Spring: Pastel candies in pink, yellow, blue, and green.
• Valentine’s Day: Red, pink, and white candies.
• Any old Tuesday: Use whatever chocolate-coated candies are already in the pantry.

Flourless Monster Cookies: Chewy Peanut Butter Oatmeal Cookies

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• Author: Joy the Baker
• Prep Time: 30 minutes
• Cook Time: 12 minutes
• Total Time: about 45 minutes
• Yield: about 16 cookies 1x
• Category: baking, cookie
• Method: Baking
• Diet: Gluten-Free

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Description

These flourless peanut butter monster cookies are thick, chewy, and packed with all the good stuff: creamy peanut butter, rolled oats, mini chocolate chips, and plenty of Reese’s Pieces (if you’re going for a Halloween / fall theme). They bake up with crisp edges, soft centers, and just enough salt to keep all that peanut butter and chocolate in check. They’re hearty and so satisfying. 

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Ingredients

Scale 1x2x3x

• 2 large eggs
• 1 cup (256 grams) creamy peanut butter, such as Jif or Skippy
• 3/4 cup (160 grams) packed light brown sugar
• 1/4 cup (50 grams) granulated sugar
• 2 teaspoons vanilla extract
• 3/4 cup (75 grams) old-fashioned rolled oats
• 1/2 teaspoon baking soda
• 1/2 teaspoon kosher salt
• 1/2 cup (85 grams) mini semisweet chocolate chips
• 1/2 cup (about 85 grams) peanut butter candies, such as Reese’s Pieces, plus a few more for topping
• Flaky sea salt, for topping, optional but highly encouraged

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Instructions

1. Place racks in the upper third and center of the oven and preheat to 350°F. Line two baking sheets with parchment paper.
2. In a large bowl, whisk the eggs until well combined and just a little frothy.
3. Add the peanut butter, brown sugar, granulated sugar, and vanilla. Use a whisk then asturdy spatula or wooden spoon to stir everything together until smooth, glossy, and thoroughly combined. The mixture will be thick and sticky.
4. Add the oats, baking soda, and salt and stir until evenly incorporated.
5. Fold in the mini chocolate chips and peanut butter candies. Try not to eat all the Reese’s Pieces before they make it into the cookies. I say this knowing full well what we’re all capable of.
6. Let the dough rest in the fridge for 20 minutes. This gives the oats a chance to soak up some of the moisture from the dough and helps the cookies bake up thick and chewy.
7. Scoop the dough into generous 2-tablespoon portions and place them about 2 inches apart on the prepared baking sheets. The dough will be sticky, so a cookie scoop is ideal here.
8. Gently press a few extra peanut butter candies and chocolate chips into the tops of each cookie.
9. Bake for 10 to 12 minutes, rotating the pans halfway through baking, until the edges are set but the centers still look slightly soft.
10. Don’t wait for these cookies to look completely done in the oven. That’s how we lose the chewy center. They’ll continue to set as they cool.
11. Sprinkle the warm cookies with flaky sea salt, if using, and allow them to cool on the baking sheet for at least 10 minutes before transferring to a wire rack.
12. The cookies will be soft while warm and settle into a chewy, peanut buttery situation as they cool.

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Notes

Use conventional creamy peanut butter. A natural peanut butter that separates into oil and peanut solids can make these cookies spread unpredictably. Jif or Skippy is exactly what we want.

For gluten-free cookies: Use certified gluten-free rolled oats and double-check the labels on your candies and chocolate chips.

Storage: Store the cookies in an airtight container at room temperature for up to 4 days. The dough can also be scooped and frozen, then baked straight from the freezer with an extra minute or two in the oven.