Chewy, peanut-buttery, and loaded with M&Ms and chocolate chips, these monster cookie bars taste like the bakery classic in soft, gooey bar form! I love that they mix up in one bowl, bake in under an hour, and skip all the chilling, scooping, and assembly that my monster cookie cupcakes need.
Thick, chewy, and full of texture in every bite, they’re the kind of nostalgic, better-than-bakery treat that disappears before they’ve even cooled.
When I’m out of M&Ms but still want a rich and decadent bar, my thick brown butter chocolate chip blondies are precisely what I make. Same soft cookie texture, just with brown butter instead!
Step-by-Step Instructions
Step 1: Cream the butter, sugar, and peanut butter. In a large mixing bowl with a hand mixer or stand mixer, cream the peanut butter, softened butter, granulated sugar, and brown sugar until light and fluffy.
Step 2: Mix in the wet ingredients. Mix in the egg, egg yolk, and vanilla extract until combined. Scrape down the bowl if necessary.
Step 3: Mix in the dry ingredients. Use a rubber spatula to fold in the flour mixture, M&Ms, and chocolate chips.
Step 4: Bake! Press the cookie dough evenly into the prepared baking pan. Sprinkle more M&Ms and chocolate chips over the top, then bake until the top and edges are golden brown. Let the pan cool on a wire rack before cutting into squares!
Mini chocolate chips and M&Ms are my not-so-secret weakness, and my soft & chewy chocolate chip M&M cookies prove it. They’re packed with the same colorful chocolatey crunch, just without the oats and peanut butter!
I know you’ll still have a bag of M&Ms lying around after you make these (guilty), lucky for you, my easy one-bowl M&M brownies are perfect for using them up!
If you tried this or any other recipe on my website, please let me know how it went in the comments; I love hearing from you! Also, please leave a star rating while you’re there! You can also tag me on Instagram or Facebook so I can check it out!
Monster Cookie Bars
Equipment
Ingredients
- 14 tablespoons unsalted butter , room temperature
- 1/2 cup creamy peanut butter
- 1/2 cup light brown sugar, packed
- 1/2 cup dark brown sugar, packed
- 1/2 cup granulated sugar
- 2 large eggs, room temperature
- 2 large egg yolks, room temperature
- 1 tablespoon vanilla extract
- 2 cups all-purpose flour, *See notes below for measuring*
- 1 3/4 cup rolled oats (old-fashioned oats)
- 1/2 cup semi-sweet chocolate chips
- 1/2 cup chopped chocolate bar
- 1/3 cup mini M&Ms
- 1/3 cup regular M&Ms
- 1 teaspoon baking soda
- 1 teaspoon fine sea salt
Instructions
- Line a 9×13 baking pan with parchment paper or grease the sides and bottom with nonstick spray or butter. Then preheat the oven to 350 F/180 C.
- In a mixing bowl, cream the butter, peanut butter, brown sugar, and granulated sugar until light and fluffy.14 tablespoons (196 g) unsalted butter, 1/2 cup (132 g) creamy peanut butter, 1/2 cup (100 g) light brown sugar, 1/2 cup (100 g) dark brown sugar, 1/2 cup (100 g) granulated sugar
- Mix in the eggs, egg yolks, and vanilla.2 (100 g) large eggs, 2 (36 g) large egg yolks, 1 tablespoon vanilla extract
- Fold in the flour, oats, baking soda, salt, chocolate chips, chopped chocolate, and M&Ms until just combined. Do not overmix! Evenly spread the cookie dough into the prepared baking pan. Sprinkle the top with extra chocolate chips, chopped chocolate, and M&Ms if desired.2 cups (260 g) all-purpose flour, 1 3/4 cup (180 g) rolled oats (old-fashioned oats), 1/2 cup (85 g) semi-sweet chocolate chips, 1/2 cup (78 g) chopped chocolate bar, 1/3 cup (75 g) mini M&Ms, 1 teaspoon baking soda, 1 teaspoon fine sea salt, 1/3 cup (78 g) regular M&Ms
- Bake in the preheated oven for 25-35 minutes or until the top is golden brown and a toothpick inserted into the center comes out just barely moist. Let them cool completely on a wire rack before cutting then enjoy!
Video
Notes
Tried this recipe?Leave a comment below & tag @cambreabakes on social!
Made these for the first football Sunday & my friends and family were so obsessed! It is literally all the things, chewy, chocolatey, full of peanut butter & candy! I love that it is an oat based bar, it gives it an amazing texture. Will definitely be making these again!
Hi! I was looking for your recipe for dirt pudding brownies as I was planning on making it but it seems to not be on the blog anymore! Are you reworking it?
Hi Maya! Unfortunately, that recipe was lost in a few website transitions and it is now lost to the web 😢
Sorry, I am confused about the metric measurements, 1-2-3 ?? If it’s all for the
same 8 + 8 size baking pan ? Please help, as I would love to make them
for my grandkids ?! I need everything in cup measurements. Also, why 2 or 3 eggs ?
The 1-2-3 is strictly for doubling or tripling the recipe. It’s default is 1x. If you want everything in cup measurements don’t click the metric button. There is only 1 egg in the recipe, not 2-3.
All of your recipes are amazing but i have to say this one is my new favorite!!! SOOO GOOD 🤤
Stop what you’re doing and make these immediately!!! Sooooo delicious, chewy, soft, chocolatey, just perfect.