Oh, let me tell you about the joy of baking! There’s something magical about filling your kitchen with the sweet aroma of freshly baked goods, and these Monster Cookie Bars are the perfect treat to create that atmosphere. Imagine all your favorite goodies – chocolate chips, M&M’s, and creamy peanut butter – coming together in one delicious dessert. It’s like a party for your taste buds! Every time I whip up a batch, I’m transported back to family gatherings where everyone gathers around, eagerly waiting for a taste. Trust me, these bars are a crowd-pleaser! They disappear faster than you can say “Monster Cookie Bars,” leaving behind happy faces and sticky fingers. Whether it’s a birthday, holiday, or just a regular Tuesday, these bars have a way of making any occasion feel special. So grab your mixing bowl, and let’s dive into making these delightful treats!

Ingredients List
Alright, let’s gather everything we need to make these scrumptious Monster Cookie Bars! Make sure you have the following ingredients ready:
- 2 cups all-purpose flour (spooned and leveled) – This helps get the right texture without making the bars too dense.
- 2 cups old-fashioned oats – These add a wonderful chewiness that you’ll absolutely love.
- 1 teaspoon baking soda – This gives our bars that nice rise.
- 1 teaspoon sea salt – Just the right amount to balance all that sweetness!
- 1 cup unsalted butter (at room temperature) – Softened butter is key for easy mixing and a rich flavor.
- 1 cup creamy peanut butter – The star of the show for that delicious nuttiness.
- 1 ½ cups packed light brown sugar – Adds a deep caramel flavor and moisture.
- ½ cup granulated sugar – For that classic sweetness that we all crave.
- 2 large eggs – These help bind everything together.
- 1 tablespoon vanilla extract – Because who doesn’t love that warm, inviting aroma?
- 1 ¼ cups semi-sweet chocolate chips – These add melty goodness in every bite.
- 1 ½ cups M&M’s, divided – A colorful touch that makes these bars extra fun!
- Flaky sea salt, for sprinkling on top – Just a pinch at the end makes all the difference.
Having everything prepped and ready to go makes the baking process so much smoother, so take a moment to gather these ingredients! Trust me, it’s worth it for these divine Monster Cookie Bars!
How to Prepare Monster Cookie Bars
Now that we have our ingredients lined up, it’s time to get into the fun part – baking these delightful Monster Cookie Bars! Don’t worry; I’ve got you covered with simple steps that will make the process a breeze. Let’s jump right in!
Step-by-Step Instructions
First things first, you’ll want to preheat your oven to 350°F. This is super important because a hot oven means your bars will bake evenly and turn out just right. While that’s heating up, grab a 9×13-inch pan and grease it generously with nonstick cooking spray. You don’t want those delicious bars sticking to the pan!
In a large mixing bowl, whisk together the flour, oats, baking soda, and salt. This dry mix is the foundation for our bars, so give it a good stir and then set it aside for now.
Next, in your stand mixer (or a large mixing bowl if you’re going old school), cream together the unsalted butter and peanut butter with both sugars until it’s smooth and creamy. This takes about 2 minutes. Make sure to scrape down the sides of the bowl to get everything mixed well. Then, add the eggs and vanilla extract, mixing until everything is combined.
Now comes the fun part! Gradually add in the dry ingredients, mixing until just combined. You’ll want to be careful here – overmixing can lead to tough bars, and nobody wants that! Once everything is incorporated, gently stir in the chocolate chips and 1 cup of M&M’s. It’s like adding little treasures that will make each bite a delight!
Spread the mixture evenly into your prepared pan, and don’t forget to sprinkle the remaining ½ cup of M&M’s on top for that beautiful pop of color. Now, it’s time to bake! Slide the pan into your preheated oven and let it bake for about 25–35 minutes, or until the bars are lightly golden brown and set. Keep an eye on them because overbaking can turn these chewy delights into something more like bricks!
Once they’re done, take them out and sprinkle a little flaky sea salt on top while they’re still warm. Let them cool completely in the pan before cutting into bars. This cooling time is crucial to ensure they hold their shape!
Tips for Success
For the best Monster Cookie Bars, consider chilling your dough for up to 48 hours before baking – it deepens the flavors and softens the oats. Remember, don’t overbake! You want that soft, chewy texture, so check them a couple of minutes before the timer goes off. Happy baking!
Nutritional Information
Now, let’s talk about the nutritional info for these delightful Monster Cookie Bars! Each bar packs a punch with approximately 389 calories, including 30 grams of sugar and 21 grams of fat. But keep in mind, these values can vary based on the specific brands and ingredients you use. So, while it’s fun to keep track of calories and nutrients, remember that baking is all about joy and indulgence! Enjoy these treats in moderation, and don’t stress too much over the numbers – happiness tastes way better!
FAQ Section
Got questions about these delicious Monster Cookie Bars? Don’t worry, I’ve got you covered! Here are some common queries that pop up when baking these treats.
Can I use different types of chocolate?
Absolutely! You can swap out semi-sweet chocolate chips for dark chocolate or even white chocolate if you want a different flavor profile. Each type of chocolate brings its unique sweetness and richness, so feel free to experiment and find your favorite combination!
How can I store leftover Monster Cookie Bars?
To keep those Monster Cookie Bars fresh and chewy, store them in an airtight container at room temperature. They’ll stay delicious for about a week. If you want to keep them longer, you can freeze them! Just wrap each bar in plastic wrap and place them in a freezer bag. They’ll be perfect for a quick treat later!
Can I make these cookie bars gluten-free?
You sure can! To make these Monster Cookie Bars gluten-free, simply substitute all-purpose flour with a 1:1 gluten-free baking blend. Just make sure that your oats are certified gluten-free, as some can be cross-contaminated. Enjoy all the flavors without the gluten!
Why You’ll Love This Recipe
- Super Easy to Make: With simple steps and common ingredients, these Monster Cookie Bars come together in no time!
- Ultimate Flavor Explosion: The combination of chocolate, peanut butter, and M&M’s creates a mouthwatering treat that satisfies every sweet tooth.
- Perfect for Any Occasion: Whether it’s a birthday party, potluck, or just a cozy night in, these bars are always a hit.
- Chewy and Delicious: The blend of oats and chocolate yields a wonderfully chewy texture that everyone loves.
- Make Ahead Option: Prep the dough in advance for a quick bake whenever the craving strikes!
Equipment List
To whip up these delightful Monster Cookie Bars, you’ll need a few essential tools. Here’s what I recommend having on hand:
- Stand mixer or a large mixing bowl and sturdy spoon – Perfect for creaming the butters and sugars.
- 9×13-inch baking pan – The ideal size for these bars!
- Whisk – For combining those dry ingredients.
- Measuring cups and spoons – Accurate measurements are key!
- Spatula – Great for spreading the batter evenly in the pan.
With these tools in your kitchen, you’ll be all set to create mouthwatering Monster Cookie Bars!
Variations
One of the best things about Monster Cookie Bars is how versatile they are! You can easily customize them to suit your taste or what you have on hand. Here are a few fun ideas to mix things up:
- Add nuts: Chopped peanuts or walnuts can add a delightful crunch and enhance the nutty flavor of the peanut butter.
- Switch up the mix-ins: Try using butterscotch chips or white chocolate instead of semi-sweet chocolate for a different flavor profile.
- Incorporate dried fruits: Raisins or cranberries can introduce a chewy texture and a hint of tartness that pairs wonderfully with the sweetness.
- Experiment with nut butter: Swap out the creamy peanut butter for almond or cashew butter for a unique twist!
Feel free to get creative and make these bars truly your own! Each variation offers a new taste adventure.

Serving Suggestions
These Monster Cookie Bars are delicious on their own, but if you want to take them to the next level, try serving them warm with a scoop of vanilla ice cream on top! A drizzle of chocolate sauce or a glass of cold milk also complements these bars perfectly. Enjoy the delightful combo!
Storage & Reheating Instructions
To keep your Monster Cookie Bars fresh and chewy, store any leftovers in an airtight container at room temperature. They’ll stay delicious for about a week, but I doubt they’ll last that long! If you want to extend their life, you can freeze them. Just wrap each bar in plastic wrap and place them in a freezer bag. When you’re ready for a treat, simply take a bar out and let it thaw at room temperature for a few hours, or pop it in the microwave for about 10-15 seconds for a warm, gooey experience. Enjoy!
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Monster Cookie Bars: 7 Delicious Secrets for Joyful Baking
- Total Time: 45 minutes
- Yield: 20 bars 1x
- Diet: Vegetarian
Description
Monster Cookie Bars are a delicious treat packed with chocolate chips, M&M’s, and peanut butter.
Ingredients
- 2 cups all-purpose flour, spooned and leveled
- 2 cups old fashioned oats
- 1 teaspoon baking soda
- 1 teaspoon sea salt
- 1 cup unsalted butter, at room temperature
- 1 cup creamy peanut butter
- 1 ½ cups packed light brown sugar
- ½ cup granulated sugar
- 2 large eggs
- 1 tablespoon vanilla extract
- 1 ¼ cups semi-sweet chocolate chips
- 1 ½ cups M&M’s, divided
- Flaky sea salt, for sprinkling on bars
Instructions
- Preheat the oven to 350°F. Grease a 9×13-inch pan generously with nonstick cooking spray.
- In a large bowl, whisk together the flour, oats, baking soda, and salt. Set aside.
- In a stand mixer, cream the butter, peanut butter, and sugars together until smooth, about 2 minutes. Scrape down the sides as needed.
- Add the eggs and vanilla extract. Mix until combined.
- Add the dry ingredients and mix until just combined. Do not overmix.
- Stir in the chocolate chips and 1 cup of M&M’s.
- Spread the mixture evenly into the prepared pan. Top with the remaining ½ cup of M&M’s.
- Bake for 25–35 minutes, or until the bars are lightly golden brown and set. Do not overbake.
- Remove from the oven and sprinkle with flaky sea salt. Let cool completely in the pan before cutting into bars.
Notes
- The dough can be prepared ahead of time and chilled for up to 48 hours.
- Chilling also softens the oats.
- Avoid overbaking to keep the bars soft and chewy.
- Prep Time: 15 minutes
- Cook Time: 30 minutes
- Category: Dessert
- Method: Baking
- Cuisine: American
Nutrition
- Serving Size: 1 bar
- Calories: 389
- Sugar: 30 g
- Sodium: 212 mg
- Fat: 21 g
- Saturated Fat: 10 g
- Carbohydrates: 46 g
- Fiber: 3 g
- Protein: 6 g
- Cholesterol: 36 mg
Keywords: Monster Cookie Bars, dessert, cookies, baking