Monster Cookie Bars
Loaded with all the yummiest fillings, these soft & chocolatey Monster Cookie Bars are the ULTIMATE sweet treat for any celebration!
This easy dessert recipe takes the cookies you love most—chocolate chip, peanut butter, oatmeal, M&M—and mixes them into scrumptious, over-the-top Monster Cookie Bars! This delicious cookie recipe starts with a classic flour, butter, sugar, and vanilla dough and blasts the batter with many fun fillings! These will disappear in a flash!
Monster Cookies are Party Favorites!
If you want the best and easiest recipe for your next birthday party or back-to-school bash, these Monster Cookie Bars can’t be beaten! Plus, this recipe makes a BIG batch! They are so fast and easy—simply mix all the ingredients together, bake, and slice!
The result is a warm, gooey, chewy, chunky, brightly colored cookie bar that even the grown-ups will love.
Other Recipes to Serve with Monster Cookies
- Rainbow Cake Mix Cookies are bright & cheerful cookies that turn any day into a party!
- Sugar Cookie Bars will become a go-to treat for your celebration occasions!
Ingredients
Dry Batter: We start this bar with all the dry ingredients for a classic cookie recipe: all-purpose flour, sea salt, baking soda, and light brown sugar, so it’s easy and pantry staple-friendly!
Wet Batter: Good cookies need eggs, unsalted butter, and pure vanilla extract for stability, creaminess, and flavor!
Monster Fillings: Now for the fun! Semi-sweet chocolate chips, mini M&Ms, creamy peanut butter (or other nut butter if you’re dealing with an allergy), and large flake oats give this cookie bar its big personality and even bigger taste!
How to Make Monster Cookie Bars
STEP ONE: Add parchment paper to a 9×13 pan, leaving high edges for easy removal. Whisk together the dry cookie base in a large bowl: flour, salt, and baking soda. Add the oats and whisk again, then set aside.
STEP TWO: In your stand mixer bowl, cream together the room-temperature butter, peanut butter, and brown sugar with the paddle attachment until smooth and uniformly colored. Add the eggs and vanilla and beat again until combined.
STEP THREE: Slowly add the dry mixture to the creamy mixture in three additions, mixing until just combined after each addition. Using a spatula, gently mix in the mini chocolate chips and most (reserve 1/4 cup) of the mini M&Ms.
STEP FOUR: Transfer the cookie batter to the parchment-lined pan and flatten. Sprinkle the top with the remaining M&Ms. Chill this cookie dough in the fridge for about an hour before baking.
STEP FIVE: Once the batter is chilled, preheat the oven to 350 degrees F with the rack in the center. Bake for 33-35 minutes until the edges are golden brown. (A toothpick inserted should be lightly moist, as there are a lot of chocolate chips and M&Ms!) Allow the pan to cool fully before lifting out the Monster Cookie and cutting it into bars. Enjoy with a cold glass of milk!
Tips for Success
- If peanut butter is an issue, substitute almond or cashew butter!
- Chilling the dough for an hour before baking allows this heavy batter to cool evenly.
- For best results, use room-temperature butter and eggs to make the dough.
- Remove cookie bars from the oven while still soft. They will continue to cook until they are cool. Overbaking will leave you with dry, crumbly cookie bars.
- A little sea salt sprinkled over the bars as soon as they are removed from the oven will add a nice grown-up counterbalance to the sweet ingredients!
What Are Monster Cookies?
Don’t confuse Monster Cookies with Magic Cookies (which have chocolate, coconut & nuts!) And Monster Cookies have nothing to do with Sesame Street, though Cookie Monster would love these!
Monster Cookies are so named because they’re loaded with fun flavors and fillings like chocolate chips, M&Ms, oatmeal, and peanut butter to make big, chunky, chewy, delicious cookies!
Can I Make Monster Cookies Ahead of Time and Freeze?
Yes! These cookie bars have so many options!
You can make the cookie dough in advance, then cover and refrigerate for up to 2 days. When ready to bake, allow the dough to come to room temperature before popping it into the oven!
You can also make & bake the bars ahead of time. Either store them in an airtight container in the pantry or on the countertop for up to 4 days. Or allow them to cool, then freeze in an airtight container for up to 3 months!
Other Crazy Good, Kid-Friendly Cookie Bar Recipes!
- No Bake Cookie Dough Bars
- Snickerdoodle Cookie Bars
- Brown Sugar Cookie Bars
- Peanut Butter & Jelly Oatmeal Bars
- Chocolate Chip Cookie S’mores Bars
- Ultimate Candy Cookie Bars
Monster Cookie Bars
Equipment
- Stand Mixer or Hand Mixer
Ingredients
- 2 cups all-purpose flour
- 1 ¼ teaspoons salt
- ½ teaspoon baking soda
- 1 ¾ cups rolled oats
- 1 cup unsalted butter at room temperature
- 1 cup creamy peanut butter
- 2 cups light brown sugar not packed
- 2 large eggs at room temperature
- ½ tablespoon vanilla extract
- 1 cup mini semi-sweet chocolate chips
- 2 cups mini M&Ms divided
Instructions
- Line a 9-inch x 13-inch metal pan with parchment paper, making sure the paper hangs over the edges. Set aside.
- In a medium mixing bowl, whisk together the flour, salt, and baking soda. Stir in the rolled oats. Set aside.
- In a stand mixer bowl with the paddle attachment, beat together the butter, peanut butter, and brown sugar until light in color, about 3 minutes.
- Add in the eggs and vanilla and beat to combine. Scrape the sides of the bowl with a rubber spatula.
- Add the flour mixture to the wet ingredients in 3 additions, mixing until just combined after each addition. Stir in the mini chocolate chips and 1 3/4 cups of the mini M&Ms with a rubber spatula.
- Transfer the dough to the prepared pan and press it into an even layer. Sprinkle the remaining mini M&Ms on top and press them into the dough slightly.
- Refrigerate for 1 hour.
- Preheat your oven to 350 degrees F with an oven rack placed in the middle position.
- Bake for 33-35 minutes until the edges are golden brown, and a toothpick inserted in the center comes out lightly moist.
- Place the pan on a wire rack to cool to room temperature. Then use the parchment paper to lift the bars from the pan. Cut into 24 squares and enjoy!
