Classic Monster Cookie Bars are thick, chewy, and loaded with peanut butter, oats, chocolate chips, and colorful candy-coated chocolates. They’re everything I love about monster cookies, but baked in a pan and cut into easy-to-serve squares. Perfect for bake sales, parties, or anytime I want a fun and satisfying treat.
Why You’ll Love This Recipe
I love how these bars bring together all my favorite cookie mix-ins in one simple, no-fuss dessert. They’re hearty from the oats, rich from the peanut butter, and full of melty chocolate and crunchy candy. Since they’re baked in one pan, there’s no need to roll dough or bake multiple batches—just mix, bake, and slice.
ingredients
(Here’s a tip: Check out the full list of ingredients and measurements in the recipe card below.)
unsalted butter
brown sugar
granulated sugar
eggs
creamy peanut butter
vanilla extract
baking soda
salt
old-fashioned oats
all-purpose flour
semi-sweet chocolate chips
candy-coated chocolates (like M&M’s)
directions
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I preheat the oven to 350°F (175°C) and line a 9×13-inch baking pan with parchment paper.
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In a large bowl, I cream together the butter, brown sugar, and granulated sugar until light and fluffy.
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I beat in the eggs one at a time, then add the peanut butter and vanilla extract and mix until smooth.
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I stir in the baking soda and salt, then gradually add the oats and flour until just combined.
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I fold in the chocolate chips and most of the candy-coated chocolates, saving a handful to press on top.
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I spread the dough evenly into the prepared pan and press the reserved candies into the surface.
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I bake for 20–25 minutes, until the edges are golden and the center is just set.
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I let the bars cool completely in the pan before slicing into squares.
Servings and timing
This recipe makes about 24 bars.
Prep time: 15 minutes
Bake time: 20–25 minutes
Cooling time: 30 minutes
Variations
Sometimes I swap the peanut butter for almond butter or sunflower seed butter if I need a nut-free version. I’ve also added chopped pretzels or coconut for extra texture. For a seasonal twist, I use holiday-colored candies or add a sprinkle of flaky sea salt on top.
storage/reheating
I store the bars in an airtight container at room temperature for up to 5 days. They also freeze well—just wrap them individually and store in a freezer bag for up to 2 months. I let them thaw at room temp or microwave for about 10 seconds to get that just-baked texture again.
FAQs
Can I use quick oats instead of old-fashioned?
Yes, I’ve done that when I’m out of old-fashioned oats. The texture is slightly softer, but still chewy and delicious.
Can I make these bars without flour?
I can use more oats in place of flour for a flourless version, though the bars will be softer and slightly more crumbly.
Do I have to chill the dough?
No chilling is needed—that’s one of the reasons I love this recipe. I mix and bake right away.
How do I keep them from overbaking?
I take them out when the edges are golden and the center looks just set. They firm up more as they cool.
Can I double this recipe?
Yes, I double it and bake in a larger sheet pan (like 11×17) or do two 9×13 pans. I keep the baking time roughly the same, just checking for doneness at the center.
Conclusion
Classic Monster Cookie Bars are one of my favorite ways to satisfy a sweet tooth with minimal effort. They’re packed with flavor, easy to share, and always a hit wherever I bring them. When I want something chewy, colorful, and chocolate-filled, this recipe never lets me down.
Print
Classic Monster Cookie Bars Recipe
- Prep Time: 15 minutes
- Cook Time: 25 minutes
- Total Time: 1 hour
- Yield: 24 bars
- Category: Dessert
- Method: Baking
- Cuisine: American
- Diet: Vegetarian
Description
Classic Monster Cookie Bars are thick, chewy bars loaded with oats, peanut butter, chocolate chips, and colorful candy-coated chocolates. They’re easy to make, fun to eat, and perfect for any crowd.
Ingredients
- 1 cup unsalted butter, softened
- 1 cup brown sugar
- 1/2 cup granulated sugar
- 2 large eggs
- 1 cup creamy peanut butter
- 1 tsp vanilla extract
- 1 tsp baking soda
- 1/2 tsp salt
- 2 cups old-fashioned oats
- 1 cup all-purpose flour
- 1 cup semi-sweet chocolate chips
- 1 cup candy-coated chocolates (e.g., M&M’s), divided
Instructions
- Preheat oven to 350°F (175°C). Line a 9×13-inch baking pan with parchment paper.
- Cream together butter, brown sugar, and granulated sugar until light and fluffy.
- Beat in eggs one at a time. Add peanut butter and vanilla, and mix until smooth.
- Stir in baking soda and salt, then add oats and flour until just combined.
- Fold in chocolate chips and most of the candy-coated chocolates, reserving some for the top.
- Spread dough evenly into the prepared pan. Press remaining candies on top.
- Bake for 20–25 minutes, until edges are golden and center is just set.
- Cool completely in the pan before slicing into bars.
Notes
- Swap peanut butter for almond or sunflower seed butter for nut-free option.
- Add chopped pretzels, coconut, or seasonal candies for variety.
- Use quick oats in place of old-fashioned oats if needed.
- Freeze individually wrapped bars for up to 2 months.
- Microwave bars for 10 seconds to enjoy warm and gooey.
Nutrition
- Serving Size: 1 bar
- Calories: 260
- Sugar: 20g
- Sodium: 140mg
- Fat: 14g
- Saturated Fat: 6g
- Unsaturated Fat: 7g
- Trans Fat: 0g
- Carbohydrates: 30g
- Fiber: 2g
- Protein: 5g
- Cholesterol: 30mg
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