Name: Monster Cookie Bars
Prep time: 15 min
Cook time: 30 min
Total time: 45 min
Cuisine: American
Ingredients: 2 cups old-fashioned rolled oats; 1 1/4 cups all-purpose flour; 1 tsp baking soda; 1/2 tsp salt; 1/2 cup unsalted butter, softened; 3/4 cup creamy peanut butter; 1 cup brown sugar; 1/2 cup granulated sugar; 2 large eggs; 2 tsp vanilla extract; 1 cup semisweet chocolate chips; 1 cup candy-coated chocolate pieces (like M&M’s), divided

Why You’ll Love This Recipe

Monster Cookie Bars are a one-bowl, no-fuss dessert that’s both fun and filling. They have everything you want in a sweet treat: chewy texture, rich peanut butter flavor, and plenty of chocolate in every bite. Whether you’re making them for a crowd or stashing them for a snack, they’re always a hit.

Ingredients

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

Old-fashioned rolled oats
All-purpose flour
Baking soda
Salt
Unsalted butter (softened)
Creamy peanut butter
Brown sugar
Granulated sugar
Eggs
Vanilla extract
Semisweet chocolate chips
Candy-coated chocolate pieces (like M&M’s)

Directions

Preheat oven: Set oven to 350°F (175°C). Grease or line a 9×13-inch baking pan with parchment paper.
Mix dry ingredients: In a medium bowl, whisk together oats, flour, baking soda, and salt.
Cream butter and sugar: In a large bowl, beat together butter, peanut butter, brown sugar, and granulated sugar until smooth and fluffy.
Add wet ingredients: Mix in the eggs and vanilla until fully incorporated.
Combine and fold: Gradually mix in the dry ingredients until combined. Fold in chocolate chips and most of the candy pieces (reserve some for topping).
Spread and bake: Spread the dough evenly in the prepared pan. Press remaining candy pieces on top. Bake for 25–30 minutes, or until golden around the edges and just set in the middle.
Cool and slice: Let the bars cool completely in the pan before cutting into squares.

Servings and timing

Servings: 20–24 bars
Prep Time: 15 minutes
Cook Time: 25–30 minutes
Total Time: About 45 minutes

Variations

Use crunchy peanut butter for added texture.
Substitute almond or sunflower seed butter for a peanut-free version.
Add chopped nuts, shredded coconut, or butterscotch chips.
Use seasonal or themed candy pieces for holidays and parties.
Add a sprinkle of flaky sea salt on top for a sweet-salty contrast.

Storage/Reheating

Store Monster Cookie Bars in an airtight container at room temperature for up to 5 days. For longer storage, freeze for up to 2 months—wrap bars individually or store in layers with parchment paper. Thaw at room temperature or microwave for a few seconds to warm.

FAQs

What are Monster Cookies?

Monster Cookies are a soft, chewy cookie made with oats, peanut butter, chocolate chips, and colorful candy-coated chocolates.

Can I make these gluten-free?

Yes, use a gluten-free flour blend and make sure your oats are certified gluten-free.

Can I use quick oats?

Old-fashioned rolled oats are preferred for texture, but quick oats will work in a pinch.

Do I have to use peanut butter?

No, you can substitute other nut or seed butters like almond or sunflower seed butter.

Can I make these bars dairy-free?

Yes, use dairy-free chocolate chips and plant-based butter.

Why are my bars dry?

Overbaking can cause dryness. Remove them from the oven when the center is just set to keep them soft and chewy.

Can I add protein powder?

Yes, you can add a scoop of protein powder. You may need to reduce the flour slightly or add a splash of milk for moisture.

How do I know when they’re done?

The edges should be golden and the center should look just set—not wet. They’ll firm up as they cool.

Can I double the recipe?

Yes, double the ingredients and use a larger pan (like 11×17-inch) or bake in two separate 9×13 pans.

What’s the best way to cut clean bars?

Let them cool completely, then use a sharp knife. Wipe the blade between cuts for clean slices.

Conclusion

Monster Cookie Bars are the ultimate comfort treat—thick, chewy, colorful, and packed with flavor. They’re perfect for sharing, storing, or customizing with your favorite mix-ins. Whether you’re baking for a crowd or just want something sweet and satisfying, these bars will never disappoint.