These Monster Cookie Bars are a chewy, delicious dessert that’s packed with peanut butter, oats, chocolate chips, and colorful M&Ms. Perfect for satisfying your sweet tooth, these bars bring the best of all your favorite cookies into one easy-to-make treat.

Why You’ll Love This Recipe

Irresistible Combination of Flavors: With peanut butter, oats, chocolate chips, and M&Ms, these bars offer a perfect balance of sweet, salty, and chewy textures.
Quick and Easy: No need for chilling dough or shaping individual cookies—just mix, bake, and enjoy!
Customizable: You can add or substitute ingredients, such as using different types of chips or adding nuts, to suit your preferences.

The BEST Monster Cookie Bars

Ingredients

1/2 cup unsalted butter, softened
1/2 cup peanut butter
1 cup brown sugar, packed
1/2 cup granulated sugar
2 large eggs
1 teaspoon vanilla extract
1 1/2 cups rolled oats
1 cup all-purpose flour
1/2 teaspoon baking soda
1/2 teaspoon salt
1/2 cup chocolate chips
1/2 cup M&Ms
1/2 cup peanut butter chips (optional)

(Tip: You’ll find the full list of ingredients and measurements in the recipe card below.)

Directions

Preheat the Oven: Set your oven to 350°F (175°C). Grease and line a 9×13-inch baking dish with parchment paper.
Prepare the Dough: In a large bowl, cream together the butter, peanut butter, brown sugar, and granulated sugar until smooth and creamy.
Add Eggs and Vanilla: Add the eggs, one at a time, mixing well after each addition. Stir in the vanilla extract.
Combine Dry Ingredients: In a separate bowl, whisk together the oats, flour, baking soda, and salt. Gradually add the dry ingredients to the wet ingredients, mixing until combined.
Add Mix-Ins: Fold in the chocolate chips, M&Ms, and peanut butter chips (if using).
Spread the Dough: Spread the dough evenly into the prepared baking dish and press it down gently with a spatula.
Bake: Bake for 18-22 minutes, or until the edges are golden and a toothpick inserted into the center comes out mostly clean (a slightly underbaked texture is fine for a chewy result).
Cool and Slice: Allow the cookie bars to cool completely before cutting them into squares.

Servings and Timing

Servings: 12 servings
Prep Time: 10 minutes
Cook Time: 20 minutes
Total Time: 30 minutes

Variations

Nutty Addition: Add 1/2 cup of chopped peanuts, walnuts, or pecans to the dough for extra crunch.
Different Chips: Use milk chocolate chips, white chocolate chips, or butterscotch chips for a fun twist.
Dried Fruit: Try adding raisins, dried cranberries, or chopped dried apricots for a fruity touch.

Storage/Reheating

Storage: Store these cookie bars in an airtight container at room temperature for up to 5 days.
Freezing: Freeze the bars in an airtight container or freezer bag for up to 2 months. Thaw at room temperature before serving.

FAQs

1. Can I use crunchy peanut butter instead of creamy?

Yes, you can substitute crunchy peanut butter, but it will add extra texture to the bars.

2. Can I use quick oats instead of rolled oats?

Rolled oats are best for this recipe as they provide a chewier texture, but quick oats will work in a pinch. Just be aware that the texture may be a bit softer.

3. Can I make these bars gluten-free?

Yes, you can use a gluten-free flour blend in place of all-purpose flour for a gluten-free version of these bars.

4. How do I prevent the bars from being too dry?

Make sure not to overbake the bars. When the edges are golden and a toothpick comes out with just a few moist crumbs, they are done. Slightly underbaking is key to keeping them chewy.

5. Can I make these bars ahead of time?

Yes, these bars can be made in advance and stored at room temperature for up to 5 days. They also freeze well.

6. Can I substitute the M&Ms with other candies?

Absolutely! You can substitute M&Ms with chocolate-covered pretzels, Reese’s Pieces, or any candy you prefer.

7. Can I add more sugar to make them sweeter?

You can add an extra 1/4 cup of sugar if you like your desserts extra sweet, but the combination of brown sugar and M&Ms should provide a balanced sweetness.

8. Can I use almond butter instead of peanut butter?

Yes, almond butter can be used as a substitute for peanut butter for a different flavor and texture.

9. How can I make these bars less sweet?

To reduce the sweetness, cut down on the sugar or use unsweetened chocolate chips instead of milk chocolate.

10. How do I know when the bars are done baking?

The bars are done when the edges are golden brown, and a toothpick inserted into the center comes out mostly clean with just a few moist crumbs. They will firm up as they cool.

Conclusion

Monster Cookie Bars are the ultimate dessert for any cookie lover! Packed with peanut butter, oats, chocolate chips, and M&Ms, they’re a chewy, indulgent treat that’s easy to make and perfect for any occasion. Whether you’re serving them at a party or simply enjoying them as a snack, these bars are sure to satisfy your sweet tooth!