Monster Cookie Bars

Monster Cookie Bars

If you can never decide between chocolate chip cookies, monster cookies, or blondies, this recipe gives you the best of all three. These Monster Cookie Bars are packed with peanut butter, hearty oats, colorful M&M's, melty chocolate chips, and sweet butterscotch chips, all baked into one thick, chewy dessert bar.

I love recipes like this because they're impossible to mess up and always a crowd favorite. Every bite is a little different depending on what mix-ins you get, which makes them just as fun to eat as they are to bake. They're the kind of dessert that's perfect for satisfying a sweet tooth.

Why You'll Love These Monster Cookie Bars

• Soft, thick, and perfectly chewy.

• Loaded with chocolate chips, butterscotch chips, and colorful M&M's.

• Peanut butter adds rich flavor and extra softness.

• Easy one-bowl recipe with simple ingredients.

• Perfect for parties, bake sales, holidays, or after-school treats.

Ingredients You'll Need

You'll only need a few pantry staples and some fun mix-ins to make these cookie bars.

• Salted butter

• Brown sugar

• Eggs

• Vanilla extract

• Creamy peanut butter

• All-purpose flour

• Baking powder

• Salt

• Rolled oats

• M&M's

• Chocolate chips

• Butterscotch chips

Scroll down to the recipe card for the full ingredient amounts and instructions.

What Makes These Bars So Good?

These bars have everything you love about a classic monster cookie, but in an easy-to-make bar form. The peanut butter and brown sugar create a rich, chewy base, while the rolled oats add just the right amount of texture.

The real magic is in the mix-ins. Chocolate chips, butterscotch chips, and M&M's make every bite a little different, so there's always something delicious waiting in the next square.

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Tips for Success

Don't Overmix the Batter

Once you add the flour, gently fold the batter until just combined. This helps keep the bars soft and chewy.

Use Old-Fashioned Rolled Oats

Rolled oats give these bars their classic monster cookie texture. Instant oats can change the consistency and aren't the best choice for this recipe.

Save a Few M&M's for the Top

Before baking, press a handful of extra M&M's into the batter. It gives the bars a colorful, bakery-style finish that's perfect for photos and serving.

Let the Bars Cool

As tempting as it is to cut into them right away, letting the bars cool helps them set and makes slicing much easier.

Storage

Store Monster Cookie Bars in an airtight container at room temperature for up to 4 days.

To freeze, wrap individual bars tightly and place them in a freezer-safe container for up to 3 months. Let them thaw at room temperature before enjoying.

Frequently Asked Questions

Can I use crunchy peanut butter?

Yes! Crunchy peanut butter adds a little extra texture and works just as well as creamy.

Can I switch up the mix-ins?

Absolutely! Try peanut butter chips, white chocolate chips, chopped pretzels, or even mini marshmallows for a fun twist.

How do I know when they're done?

The edges should be lightly golden, and the center should look set. A toothpick inserted into the center should come out with a few moist crumbs.