Monster cookie bars are the ultimate comfort food mash-up. They combine three classic American cookies into one: oatmeal, peanut butter, and chocolate chip!
And because I’m always a bit extra, I don’t stop there. I also load them down with chocolatey M&Ms for extra yumminess.
These monster cookie bars are crunchy, chewy, sweet, and satisfying.
It doesn’t matter what someone’s favorite cookie is. They can probably find it in these!
Why You’ll Love These Monster Cookie Bars
Easy Crowd-Pleaser: These colorful, fun cookie bars will satisfy anyone’s sweet tooth. They have a little something for everyone.
Simple to Make: This recipe features readily available ingredients and straightforward instructions. These little guys are a breeze to whip up, even for novice bakers.
Delightfully Indulgent: The rich, buttery dough is loaded with sweet mix-ins. These bars are totally indulgent and downright addictive.
Visually Appealing: The colorful M&Ms on top make these bars look as good as they taste. They’re striking, fun, and festive.
Ingredients
- Creamy Peanut Butter: For that rich, nutty flavor profile all peanut butter cookies have. It also holds everything in place.
- Unsalted Butter: For a moist, tender texture. Set it out early to soften.
- Sugars: Use a combo of granulated and light brown sugars. They add sweetness and provide a subtle molasses flavor.
- Large Eggs: Another binding agent. They also add moisture and provide the ultimate chewy texture. Use room-temperature eggs for the best results.
- Vanilla Extract: A flavor enhancer that adds warmth and a sweet aroma.
- All-Purpose Flour & Baking Soda: For structure and lift.
- Old-Fashioned Oats: For texture, heartiness, and a nutty taste.
- Salt: Add a little to balance the sweetness and heighten the peanut butter flavor.
- Semi-Sweet Chocolate Chips: The classic chocolate chip cookie ingredient! They add rich, gooey chocolate to every bite.
- M&Ms: The colorful, crunchy, candy-coated topping takes these over the top. Use regular or mini M&Ms, as you prefer.
How to Make Monster Cookie Bars
Follow these steps to make monster cookie bars:
1. Prepare. Preheat the oven to 350 degrees Fahrenheit. Grease a 9×13-inch baking pan. Set aside.
2. Cream the butter and sugar. Use a large bowl and mixer or a stand mixer. Cream both sugars with the butter until light and fluffy.
3. Add the eggs. Mix in one egg at a time until they’re all incorporated. Then, beat in the vanilla extract and peanut butter until smooth.
4. Finish the batter. Whisk the flour, oats, baking soda, and salt in a separate bowl. Then, gradually stir this mixture into the bowl with the eggs, butter, etc. Lastly, fold in the chocolate chips and 1 cup of M&Ms.
5. Bake. Press the dough evenly into the prepared pan and top with the remaining M&Ms. Bake for 25 to 30 minutes or until done.
6. Cool and serve. Let the bars cool completely in their pan. Then, slice, serve, and enjoy!
Tips For the Best Monster Cookie Bars
Want a few of my best cookie-making tips? I’ve got you!
- Avoid natural peanut butter. It can separate and won’t bind the other ingredients together as well. Just pick up a regular jar of creamy peanut butter.
- Don’t overmix! Mix gently and stop when everything is just incorporated. If you overmix, the bars will come out tough.
- Pack the sugar tightly! None of the other ingredients require packing. For the brown sugar, pack it to get the right amount.
- Go the old-fashioned route. Use old-fashioned oats. Quick-cooking or instant oats won’t provide the same texture.
- Keep your knife clean. When slicing the bars, wipe the knife clean between each cut. Doing so will ensure your cuts are neat and even and that the knife won’t stick.
- Toss in more add-ins. In addition to the M&Ms, you can add chopped nuts, peanut butter chips, or toffee bits. Or you can swap the M&Ms for Reese’s Pieces or chopped pieces of your favorite candy.
How to Store
These bars keep and even freeze nicely. So, if you want to double the recipe to make a big batch, go right ahead!
To Store: Store cooled monster cookie bars in an air-tight container. They’ll remain fresh for 5 days at room temperature or up to a week in the fridge.
To Freeze: Wrap individual bars tightly in plastic wrap. Then, transfer them all to a freezer-safe container. Freeze for up to 3 months. Let thaw overnight before serving.
Monster Cookie Bars
24
servings10
minutes30
minutes389
kcalMonster cookie bars are pure delight! Packed with oats, peanut butter, chocolate chips, and M&Ms, every bite is a perfect mix of chewy and crunchy.
Ingredients
1 cup (2 sticks) unsalted butter, softened
1 cup granulated sugar
1 cup light brown sugar, packed
2 large eggs
1 tablespoon vanilla extract
1 cup creamy peanut butter (not natural)
2 cups all-purpose flour
2 cups old-fashioned oats
1 teaspoon baking soda
1/2 teaspoon salt
1 cup semi-sweet chocolate chips
1 1/4 cups M&M’s candies, divided
Instructions
- Preheat oven to 350 degrees Fahrenheit. Grease a 9×13-inch baking pan and set aside.
- In a large bowl or stand mixer, cream together the butter, granulated sugar, and brown sugar until light and fluffy, about 2-3 minutes.
- Add the eggs one at a time, mixing well after each addition. Beat in the vanilla extract and peanut butter until smooth.
- In a separate bowl, whisk together the flour, oats, baking soda, and salt. Gradually stir the dry ingredients into the wet ingredients until just combined.
- Stir the chocolate chips and 1 cup of the M&M’s gently into the batter.
- Press the dough evenly into the prepared pan. Sprinkle the remaining 1/4 cup M&M’s on top and gently press into the dough.
- Bake for 25-30 minutes until the edges are lightly golden brown. Or until a toothpick inserted into the center comes out mostly clean.
- Allow the bars to cool completely in the pan before slicing and serving.
Can you make instead of bars
Hi, Brenda.
Were you asking about making cookies (like round cookies?) instead of bars?
If so, yes, you can. You’ll just need to make a few adjustments.
1. Instead of pressing the dough into a pan, scoop it into balls and place them on parchment-lined baking sheets. Use about 2 tablespoons of dough per cookie. Then, flatten the dough balls slightly with your palm or the bottom of a glass.
2. Reduce the baking time to…. hmmm… my guess would be about 10-12 minutes, as individual cookies will bake faster than bars. They’re done when the edges are lightly golden brown. (I’m not 100% sure on the exact amount of time needed, so keep an eye on them to prevent burning.)
3. Let the cookies cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.