Name: Monster Cookie Dough Brownies
Prep time: 20 min
Cook time: 30 min
Total time: 2 h
Cuisine: American
Ingredients: 1 box brownie mix; Ingredients listed on the brownie box (typically oil, eggs, and water); 1 cup rolled oats; 1/2 cup creamy peanut butter; 1/4 cup coconut oil or butter, melted; 1/2 cup brown sugar; 2 tablespoons milk of choice; 1 teaspoon pure vanilla extract; 1/2 teaspoon salt; 1/2 cup mini M&M’s; 1/3 cup chocolate chips; 1/2 cup oat flour (or all-purpose flour); 3/4 cup chocolate chips (for ganache); 1/4 cup milk of choice (for ganache)

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These Monster Cookie Dough Brownies are the ultimate dessert mashup I can’t get enough of. With a rich, fudgy boxed brownie base, a thick layer of peanut butter oatmeal cookie dough (packed with M&M’s and chocolate chips), and a silky chocolate ganache topping, every bite hits that perfect mix of gooey, chewy, and chocolatey. It’s a no-fuss treat that tastes like a bakery-level indulgence—without the bakery effort.

Monster Cookie Dough Brownies

Ingredients

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

For the Brownie Base:

1 box brownie mix

Ingredients listed on the box (typically oil, eggs, and water)

For the Monster Cookie Dough Layer:

1 cup rolled oats

½ cup creamy peanut butter

¼ cup coconut oil or butter, melted

½ cup brown sugar

2 tablespoons milk of choice

1 teaspoon pure vanilla extract

½ teaspoon salt

½ cup mini M&M’s

⅓ cup chocolate chips

½ cup oat flour (or all-purpose flour, if preferred)

For the Ganache:

¾ cup chocolate chips

¼ cup milk of choice

Directions

I preheat the oven to 350°F (175°C) and prepare the brownie batter as directed on the box. Then I spread it in a greased 9x9-inch baking pan and bake according to the package instructions. After baking, I let the brownies cool completely.

While the brownies cool, I make the monster cookie dough. In a large bowl, I mix the melted coconut oil (or butter), peanut butter, brown sugar, milk, vanilla, and salt until smooth.

Then I stir in the rolled oats, oat flour, M&M’s, and chocolate chips until everything is well combined. I gently press the cookie dough over the cooled brownie base.

For the ganache, I melt ¾ cup chocolate chips with ¼ cup milk in the microwave in 30-second intervals, stirring between each until smooth and creamy.

I pour the ganache over the cookie dough layer, spreading it evenly. Then I refrigerate the pan for at least 1–2 hours until the layers are fully set.

Once chilled and firm, I slice the brownies into squares and serve.

Servings and Timing

Servings: 16 squares

Prep Time: 20 minutes

Cook Time: 30 minutes

Chill Time: 1–2 hours

Total Time: About 2 hours (including chill time)

Calories: Approximately 320 kcal per serving

Variations

I sometimes swap the M&M’s for chopped Reese’s Pieces or mini peanut butter cups for even more peanut butter flavor.

For a gluten-free version, I use certified gluten-free oats and oat flour.

I like to make a darker version by using dark chocolate chips and reducing the sugar slightly in the cookie dough.

For a nut-free option, I use sunflower seed butter instead of peanut butter and skip the M&M’s if needed.

Storage/Reheating

I store these brownies in an airtight container in the fridge for up to 5 days. They also freeze well—just wrap individual squares in plastic wrap and store them in a freezer-safe bag or container for up to 2 months. I let them thaw at room temperature or give them a few seconds in the microwave if I want that warm, gooey texture again.

FAQs

What type of brownie mix should I use?

I usually use a fudgy-style boxed brownie mix for the richest base, but any standard 18–20 oz box will work. Just follow the package directions for best results.

Can I eat the cookie dough layer raw?

Yes! This cookie dough is egg-free and uses heat-treated oat flour or all-purpose flour, making it safe to eat without baking.

Can I make these brownies ahead of time?

Absolutely. I often make them a day in advance so they have time to chill and set up nicely before slicing. They actually taste even better the next day.

What can I use instead of oat flour?

I swap in all-purpose flour if I don’t have oat flour on hand. Almond flour works too, but it gives a slightly different texture.

Can I double this recipe?

Yes, I double everything and use a 9x13-inch pan. Just keep an eye on the bake time for the brownies and allow a bit more chill time in the fridge.

Conclusion

Monster Cookie Dough Brownies are one of my go-to desserts when I want something indulgent, fun, and crowd-pleasing. That chewy, chocolatey cookie dough on top of rich brownies, all finished with silky ganache—every layer brings something special. Whether I'm baking for a party or just treating myself, this recipe always hits the sweet spot.

Recipe:

Monster Cookie Dough Brownies

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Author: Cheryl
Total Time: 2 hours
Yield: 16 squares
Diet: Vegetarian

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Description

These Monster Cookie Dough Brownies are a rich, indulgent dessert featuring a fudgy boxed brownie base, a no-bake monster cookie dough layer with peanut butter, oats, M&M's, and chocolate chips, and a silky chocolate ganache topping. Perfect for parties or a sweet treat, they're easy to make and totally irresistible.

Instructions

Preheat oven to 350°F (175°C) and prepare brownie batter as directed on the box.
Spread brownie batter in a greased 9x9-inch baking pan and bake according to package instructions. Let cool completely.
In a large bowl, mix melted coconut oil (or butter), peanut butter, brown sugar, milk, vanilla, and salt until smooth.
Stir in rolled oats, oat flour, mini M&M’s, and chocolate chips until well combined.
Gently press the monster cookie dough evenly over the cooled brownie base.
In a microwave-safe bowl, melt ¾ cup chocolate chips with ¼ cup milk in 30-second intervals, stirring between each, until smooth.
Pour ganache over the cookie dough layer and spread evenly.
Refrigerate the pan for at least 1–2 hours until fully set.
Once firm, slice into squares and serve.