Chewy, classic monster cookies are simple and delicious! These easy oatmeal cookies are loaded with peanut butter, peanuts, pretzels and M&Ms and can be made year-round or dressed up as festive Christmas monster cookies.

There are So Many Reasons to Love These Cookies!

These monster cookies are thick, chewy, and packed with everything people love—oats, peanut butter, chopped peanuts, chocolate, and colorful candy.

This vast array of ingredients gives that "surprise in every bite" you love with a fun, colorful cookie. They're perfect for families, classrooms, and holiday baking. And trust me when I say they are loved by kids of all ages. (I could eat these every day!)

You can make these Monster Cookies in their classic and colorful style for year-round treats or switch to red and green M&Ms for a festive Christmas version. In fact, you can change up the M&Ms for nearly every holiday!

What are we waiting for? Let's bake some cookies!

Monster Cookie Ingredients

You will find a printable recipe card at the bottom of this post but here's a glance at what you will need. These are fun (and simple) ingredients you might already have on hand in your pantry or refrigerator.

• 1 cup butter, softened
• 1 cup granulated sugar
• 1 cup packed brown sugar
• ¾ cup creamy peanut butter (not pictured)
• 2 large eggs
• 1 teaspoon vanilla extract
• 1½ cups quick oats
• 1½ cups all-purpose flour
• 1 teaspoon baking soda
• ½ teaspoon salt
• 1 cup peanuts
• ½ cup chopped pretzels
• 1½ cups M&Ms (minis are best)

How to Make Monster Cookies

These come together so easily! And trust me when I say they're absolutely delicious (and hearty!) Here's how you're going to do it.

Preheat oven to 350°F. Line baking sheets with parchment paper or silicone mats.

In a large bowl, cream together the butter, granulated sugar, and brown sugar until light and fluffy.

Beat in the peanut butter, then add the eggs and vanilla, mixing until smooth.

In a separate bowl, whisk together the oats, flour, baking soda, and salt.

Gradually add the dry ingredients to the wet ingredients, mixing just until combined.

Fold in the peanuts, crushed pretzels, and M&Ms.

Scoop dough into 2–3 tablespoon mounds and place on prepared baking sheets, spacing about 2½ inches apart.

Refrigerate tray for about 10 minutes. (If you prefer, you can refrigerate the dough in the bowl for about 30 minutes before scooping. I just like to make up my trays and stick them in the fridge while the tray ahead of it is baking.)

Gently press a few extra M&Ms on top for a bakery-style look.

Flatten slightly with palm.

Bake for 10–12 minutes, just until the edges are set and the centers still look soft.

Cool on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely.

Serve and enjoy!

🧊 Storage Tips

• Store cookies in an airtight container at room temperature for up to 4 days
• Freeze baked cookies for up to 2 months
• Dough balls can be frozen and baked straight from the freezer (add 1–2 minutes to bake time)

What to Expect from Classic Monster Cookies

These monster cookies are everything a classic cookie should be—soft, chewy, and loaded with goodness. Whether you bake them for Christmas or keep them colorful year-round, they’re guaranteed to disappear fast.

I'm a fan of oatmeal cookies (and "chunky" cookies, in general) so the oats, peanuts, and pretzels gave these the crunch I was longing for. Coupled with chocolate? Well, all I can say is, these will be a staple every year! They're truly a crowd pleaser!

And like I mentioned above, they're great for a variety of occasions.

Christmas Monster Cookie Variation

• Use red and green M&Ms
• Press a few extra candies on top right after baking for color
• Optional: sprinkle lightly with flaky sea salt for contrast

Valentine Monster Cookie Variation

• Use red, white, and pink M&Ms
• Throw in some sprinkles for even more color.
• Choose red/white chocolate chips.

Frequently Asked Questions

Are Monster Cookies always made with peanut butter?

Yes — peanut butter is a defining ingredient of traditional Monster Cookies. It adds flavor, structure, and richness.

Can I use rolled oats instead of quick oats?

Yes. Pulse rolled oats once or twice in a food processor for a better texture.

Can I double this recipe?

Absolutely—use a rimmed sheet pan and check for doneness after 18–20 minutes.

Can I add more chocolate?

Yes! Add up to 2 cups total mix-ins without affecting structure.

Other Colorful Cookies from Out of the Box

If you love this recipe you're going to flip over some of our other colorful cookies. Here are some of our favorites:

Soft & Chewy M&M Cookies: Simple and delicious!

Double Dark Chocolate Peppermint Cookies: We love these! They're gorgeous and so yummy!

Strawberry Lemonade Crinkle Cookies: These start with a cake mix. (Two mixes, actually!)

Crumble Birthday Cake Cookies: So pretty! Almost too pretty to eat!

Cut-Out Sugar Cookies: These are our go-to cookies at Out of the Box Baking. . .for a reason!

That's it for this post, friends!

If you make this recipe and enjoy it, please leave a review or comment. And before you go, why not pin some photos to your Pinterest boards?

About the Baker

Hi, I’m Janice — the baker behind Out of the Box Baking. I love classic, nostalgic desserts that bring people together, and Monster Cookies have always been one of those crowd-pleasing favorites. There’s something so comforting about the combination of peanut butter, oats, chocolate chips, and colorful candies — it’s a recipe that never fails to make people smile.