Don’t Miss This Foolproof Monster Cookie Recipe At Your Next Party

There’s always that one cookie that vanishes before the tray hits the table—this is that cookie. A good monster cookie recipe doesn’t mess around with subtlety; it’s big, bold, and unapologetically over-the-top. People want it because it checks every craving in one ridiculous bite. It’s also party-proof—no fragile fluff, no weird ingredients, just chaos that works. So if you’re looking to show up with something that actually gets talked about, start here.

Ingredients in Monster Cookie Bars

To make Monster Cookie Bars, you’ll need ¾ cup of softened unsalted butter, 1⅔ cups of granulated sugar, and 1 cup of peanut butter for a rich and chewy base. Mix in 2 eggs and 2 teaspoons of vanilla extract, then combine with 1½ cups of all-purpose flour, 1¼ teaspoons of baking powder, and ½ teaspoon of salt. Stir in 1 cup of M&M’s, ⅔ cup of quick oats, and ½ cup of semi-sweet chocolate chips for added texture and bursts of sweetness. These bars are the perfect mix of creamy, crunchy, and chocolaty.
Get the Recipe: Monster Cookie Bars

Prep the Oven and Pan

Preheat your oven to 350°F. Line a 9×13-inch pan with parchment paper and set aside.

Cream the Wet Ingredients

In a stand mixer with a paddle attachment, beat softened butter until smooth. Add sugar and mix until light and fluffy. Blend in peanut butter, then add eggs and vanilla, scraping down the sides as needed.

Add Dry Ingredients and Mix-ins

Mix in the dry ingredients, followed by oats and chocolate chips. Gently fold in the M&M candies by hand to avoid breaking them.

Bake and Cool

Spread the dough evenly in the prepared pan. Bake for 25 minutes, then cover with foil and bake 10 minutes more, or until the center is set and the edges are golden. Let cool completely before slicing into bars.

Variations and Substitutions for Monster Cookie Bars

Monster cookie bars are easy to customize with whatever you have on hand. Swap semi-sweet chocolate chips for dark or milk chocolate, or use a mix of both. You can also switch up the mix-ins—try adding pretzel pieces, butterscotch chips, or raisins for extra texture and flavor. For a playful twist, cut the bars into triangles or use themed M&Ms to match different holidays. To elevate the look, drizzle melted chocolate over the top before serving.

Tips and Tricks for Making the Best Cookie Bars

To keep your M&M’s looking colorful and whole, mix them in by hand at the very end—your mixer will crush them otherwise. Only mix the dough until the flour, oats, and chocolate chips are just combined; overmixing can lead to crumbly bars. Since ovens and pans vary, check the bars at the 25-minute mark to avoid overbaking, which can dry them out. Aim for edges that are slightly crisp and centers that stay chewy. Once baked, store them covered at room temperature for up to 5 days, or freeze them for up to 2 months.
Get the Recipe: Tips and Tricks for Making the Best Cookie Bars