If you love a cookie that’s packed with everything good—chocolate, peanut butter, oats, and those colorful M&Ms—you’re going to go crazy for The Best Monster Cookie Bars Recipe. I absolutely love how these bars come out chewy, slightly crisp on the edges, and loaded with so much texture and flavor that each bite feels like a little celebration. Whether you’re making them for a potluck, school treat, or just an afternoon pick-me-up, these bars always steal the show. Keep reading, because I’ll share tips to make them perfect and customizable for your own kitchen!
Why You’ll Love This Recipe
- Super Chewy Texture: The oats combined with peanut butter give these bars a satisfying chew you won’t find in regular cookie bars.
- Loaded with Mix-ins: Chocolate chips and M&Ms make each bite exciting and colorful—you can’t help but smile while eating them.
- Easy to Make: From start to finish, this recipe takes under an hour and doesn’t require any fancy techniques.
- Totally Customizable: Swap nut butters and candy mix-ins easily to fit your preferences or dietary needs.
Ingredients You’ll Need
You’ll find that this combination of pantry staples and mix-ins strikes the perfect balance—sweet, nutty, and hearty. I always recommend using creamy nut butters so your bars come out nice and tender. Also, grabbing good-quality chocolate chips really makes a difference.
- Unsalted butter: Using unsalted lets you control the saltiness while the butter adds richness and moisture.
- Peanut butter or nut butter alternative: Creamy peanut butter is my go-to, but I love swapping it for almond or sunflower butter for allergy-friendly options.
- Brown sugar: Adds deep molasses flavor and helps keep the bars chewy.
- Granulated white sugar: Gives just a touch of crispness on the edges.
- Eggs: Acts as the binder, holding everything together flawlessly.
- Vanilla extract: This tiny splash enhances all the flavors beautifully.
- All-purpose flour: Provides the structure for the bars.
- Old fashioned oats: The heart of monster cookies—the chewy texture and nutty flavor.
- Baking soda: Helps the bars rise slightly and stay tender.
- Salt: Balances the sweetness and enhances flavors.
- Semi-sweet chocolate chips: Melty pockets of chocolate that make these bars irresistible.
- M&M candies: Fun colors and a little crunch that everyone loves.
Variations
I’m all about making recipes your own. Over time, I started swapping different mix-ins depending on what I have handy or what flavor combinations I’m craving. Feel free to get creative—you’ll find that this batter is super forgiving and adaptable.
- Peanut Butter Alternatives: I switched to Wow Butter for peanut-free guests and was amazed at how close it tastes and feels in the bars.
- Chip Swaps: Sometimes I replace half the chocolate chips with butterscotch or peanut butter chips—giving the bars a fun twist.
- Add Nuts: Adding chopped pecans or walnuts adds extra crunch and a toasty flavor I really enjoy, especially in fall.
- Mini M&Ms: If you want the bars to cut more cleanly or just prefer smaller bursts of candy, mini M&Ms are perfect!
- Cookie Version: You can also make traditional monster cookies with this dough—just scoop onto a lined sheet and bake 10-12 mins.
How to Make The Best Monster Cookie Bars Recipe
Step 1: Prep Your Pan and Oven
Go ahead and preheat your oven to 350°F (175°C). Spray or grease a 9×13 inch baking dish so your bars come out easily without sticking. I like using a non-stick baking spray that contains flour, but butter with a dusting of flour works great too. Set it aside while you whip up the dough.
Step 2: Cream Your Butters and Sugars
Using a stand mixer or hand mixer, cream together the softened butter, peanut butter, brown sugar, and granulated sugar until smooth and creamy—about 2 minutes. Don’t rush this step; well-creamed butter and sugar give your bars a light texture. Be sure to scrape down the bowl sides once or twice so everything blends evenly.
Step 3: Add Eggs and Vanilla
Mix in the eggs one at a time, blending well after each addition to incorporate fully. Then stir in the vanilla extract. These ingredients bind your dough and enhance the rich flavor, so don’t skip or substitute here if you can avoid it!
Step 4: Combine Dry Ingredients and Mix In
In a separate bowl, whisk together the flour, oats, baking soda, and salt. Then add the dry mix to the wet, blending on low speed just until combined—don’t overmix, or your bars could turn dense. After that, gently fold in the chocolate chips and M&Ms using a spatula, spreading them evenly through the dough.
Step 5: Bake and Cool
Press your dough evenly into the prepared baking pan with a spatula. Bake for about 30 to 35 minutes until the edges are golden and the top feels set but still soft to touch. I learned the hard way not to overbake because the bars will continue to firm up as they cool—so keep an eye on them starting at 28 minutes. Let them cool a bit before cutting so they don’t crumble.
Pro Tips for Making The Best Monster Cookie Bars Recipe
- Use Room Temperature Butter: It creams more easily with sugars, giving a lighter, creamier dough.
- Don’t Overmix the Dry Ingredients: Mixing just until combined keeps the bars tender and chewy, not tough.
- Press Dough Evenly: This ensures uniform baking and consistent texture in every bar.
- Watch Your Bake Time Closely: Removing the bars just as they set prevents dryness—residual heat finishes the bake.
How to Serve The Best Monster Cookie Bars Recipe
Garnishes
I usually keep things simple: a little extra sprinkle of mini M&Ms on top just before baking adds a fun pop of color and invites everyone to dig in. For special occasions, a light dusting of powdered sugar or a drizzle of melted chocolate makes these bars look irresistible on a dessert platter.
Side Dishes
These bars are a sweet treat on their own but pairing them with a cold glass of milk or a scoop of vanilla ice cream elevates the experience. Sometimes I serve them alongside fresh fruit or a hot cup of coffee for a perfect cozy snack time.
Creative Ways to Present
For birthday parties or holidays, I’ve lined a wooden serving board with parchment and stacked the bars in a pyramid shape—super inviting and perfect for sharing. Wrapping individual bars in parchment with a twine bow makes a charming edible gift for friends or coworkers.
Make Ahead and Storage
Storing Leftovers
I store leftover monster cookie bars in an airtight container at room temperature for up to 4 days, and they stay perfectly soft and chewy. If your kitchen is warm, popping them in the fridge is fine, though it can slightly firm up the texture.
Freezing
These bars freeze beautifully! I like to wrap individual pieces tightly in plastic wrap, then place them in a freezer-safe bag. When I want a quick treat, I just unwrap one and let it thaw at room temperature or gently microwave it for 10 seconds—super convenient.
Reheating
To reheat, a quick zap in the microwave (about 10-15 seconds) restores that fresh-from-the-oven softness. If you prefer, warming them briefly in a low oven (300°F) wrapped in foil works well without drying out the bars.
FAQs
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Can I use crunchy peanut butter instead of creamy?
It’s best to stick with creamy peanut butter or a smooth nut butter alternative for this recipe. Crunchy nut butters can make the texture a bit uneven and affect how the bars hold together. If you love crunch, consider adding chopped nuts separately instead!
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What if I don’t have M&Ms—can I substitute something else?
Absolutely! You can swap M&Ms for mini chocolate chips, Reese’s Pieces, or other colorful candy-coated chocolates. Even adding dried fruit or nuts works for a different flavor profile.
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Can I make these bars gluten-free?
Yes! Use gluten-free all-purpose flour and certified gluten-free oats to make this recipe safe for gluten sensitivities. The texture might be slightly different but still delicious.
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How do I know when The Best Monster Cookie Bars Recipe is done baking?
Look for golden edges and a set, slightly soft center. The bars will firm up as they cool, so avoid baking until completely hard. A gentle touch or a toothpick test can help confirm they’re just right.
Final Thoughts
I’ve made The Best Monster Cookie Bars Recipe countless times, and honestly, it still feels like a treat every single time. What I love most is how easy it is to throw together with ingredients you probably already have, yet it tastes like something special made from scratch. Whenever I bring these bars to gatherings, my family and friends go crazy for them—they’re a true crowd-pleaser. If you’re looking for a no-fail, fun, and absolutely delicious cookie bar recipe, give this one a try. I promise you’ll want to make them again and again!
Print
The Best Monster Cookie Bars Recipe
- Prep Time: 10 minutes
- Cook Time: 35 minutes
- Total Time: 45 minutes
- Yield: 24 bars
- Category: Dessert
- Method: Baking
- Cuisine: American
Description
These Best Monster Cookie Bars combine the classic flavors of peanut butter, oats, and chocolate into a chewy, flavorful treat. Loaded with peanut butter, brown sugar, oats, chocolate chips, and M&Ms, these bars are perfect for satisfying your sweet tooth. Easy to make with simple ingredients and baked to golden perfection, they offer a delightful texture and a nostalgic taste loved by all.
Ingredients
Wet Ingredients
- 1 cup unsalted butter (2 sticks), softened
- 1 cup peanut butter or nut butter alternative*
- 2 eggs
- 2 teaspoons vanilla extract
Dry Ingredients
- 1 cup packed brown sugar
- 3/4 cup granulated white sugar
- 2 cups all purpose flour
- 2 cups old fashioned oats
- 1 teaspoon baking soda
- 1/2 teaspoon salt
Add-ins
- 1 cup semi-sweet chocolate chips
- 1 cup M&M candies
Instructions
- Preheat Oven and Prepare Pan: Preheat your oven to 350°F (175°C) and lightly spray a 9×13 inch baking dish with cooking spray to prevent sticking.
- Cream Butter, Peanut Butter and Sugars: In a large bowl, use an electric mixer to beat the softened butter, peanut butter, brown sugar, and granulated sugar together until the mixture is smooth and creamy, about two minutes. Be sure to scrape down the sides of the bowl to incorporate all ingredients evenly.
- Add Eggs and Vanilla: Add the eggs and vanilla extract to the creamed mixture and continue mixing until everything is fully blended.
- Combine Dry Ingredients: In a separate bowl, combine the all-purpose flour, oat flakes, baking soda, and salt. Slowly add these dry ingredients to the wet mixture, mixing on low speed until just combined to avoid overmixing.
- Mix in Chocolate Chips and M&Ms: Gently fold in the semi-sweet chocolate chips and M&M candies to evenly distribute them throughout the dough.
- Press Dough into Pan: Transfer the dough to the prepared baking dish and use a spatula to press and smooth the dough evenly across the bottom for uniform thickness.
- Bake: Place the pan in the preheated oven and bake for 30 to 35 minutes, or until the bars turn golden brown and are set in the center. Take care not to overbake to keep the bars chewy.
- Cool and Serve: Allow the bars to cool slightly in the pan before cutting into squares and serving. This helps them firm up and makes slicing easier.
Notes
- You can switch the mix-ins: replace chocolate chips with peanut butter chips, butterscotch chips, dark chocolate chips, or nuts like walnuts or pecans.
- Use different candies instead of M&Ms or use mini M&Ms for smaller bites.
- For a peanut-free version, substitute peanut butter with creamy nut butters such as almond butter, cashew butter, or soy-based alternatives like Wow Butter. Sunflower seed butter also works but has a unique flavor.
- This dough can also be used to make individual monster cookies by scooping onto a parchment-lined baking sheet and baking at 350°F for 10-12 minutes until just set.
- Store any fully cooled bars or cookies in an airtight container at room temperature for up to four days.
Nutrition
- Serving Size: 1 bar (approx. 1/24th of recipe)
- Calories: 220
- Sugar: 14g
- Sodium: 120mg
- Fat: 12g
- Saturated Fat: 5g
- Unsaturated Fat: 6g
- Trans Fat: 0g
- Carbohydrates: 26g
- Fiber: 2g
- Protein: 5g
- Cholesterol: 35mg
