Monster Cookie Bars Recipe

If you’re on the hunt for a dessert that’s equal parts chewy, chocolatey, and downright irresistible, then you’re going to want to stick around for this Monster Cookie Bars Recipe. Trust me, these bars are an absolute game-changer — loaded with oats, peanut butter, chocolate chips, and colorful M&M’s, they hit all the right notes and are perfect for sharing (or not!). If you love a cookie bar that’s chewy with little bursts of chocolate and peanut butter flavor, stick with me — I’ll walk you through every step, and you’ll be a kitchen hero in no time.

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Ingredients You’ll Need

This Monster Cookie Bars Recipe uses classic pantry staples that blend perfectly to create a soft yet sturdy bar. The combination of flour and oats gives you that lovely chewiness, while peanut butter and chocolate chips bring all the flavor-packed richness you want. I recommend using good-quality peanut butter and fresh oats for the best results.

• All-purpose flour: Spoon and level the flour for accuracy to keep the bars from turning out dense or dry.
• Old fashioned oats: These give you chewy texture and help hold the bars together beautifully.
• Baking soda: Just a little lift to keep the bars from getting too heavy.
• Sea salt: Balances the sweetness and brings out the peanut butter flavor; flaky sea salt is perfect for sprinkling on top at the end.
• Unsalted butter: Use room temperature butter to cream smoothly with the sugars for a tender crumb.
• Creamy peanut butter: The star of the show! Make sure it’s fresh and stir it well before measuring.
• Light brown sugar: Adds moisture and that hint of molasses flavor that works so well here.
• Granulated sugar: Gives a bit of crispness to the edges once baked.
• Large eggs: They bind everything together and add structure.
• Vanilla extract: A simple addition that deepens the overall flavor.
• Semi-sweet chocolate chips: I like to use good quality chips so they melt evenly, giving gooey chocolate pockets.
• M&M’s (divided): These bring a fun pop of color and sweetness; adding some on top before baking keeps them vibrant.
• Flaky sea salt (for sprinkling): Adds a sophisticated salty crunch on top – don’t skip this little flourish!

Variations

One thing I love about this Monster Cookie Bars Recipe is how easy it is to customize. I often swap out M&M’s for other candies or nuts depending on what I have on hand. That’s the beauty of these bars — they’re a perfect base to make your own.

• Add Nuts: I sometimes toss in chopped walnuts or pecans for extra texture and a nutty depth that pairs beautifully with the peanut butter.
• Switch Up the Candy: Try peanut butter chips, butterscotch chips, or even crushed candy bars instead of M&M’s – each time you get a new twist!
• Make It Gluten-Free: Substitute the all-purpose flour with a gluten-free blend and check your oats are certified gluten-free to keep everyone happy.
• Lower Sugar Version: You can reduce the granulated sugar a bit or use natural peanut butter with no added sugar if you’re looking for a slightly healthier version.

How to Make Monster Cookie Bars Recipe

Step 1: Prep and Mix Dry Ingredients

Start by preheating your oven to 350°F (175°C) and generously greasing a 9×13-inch baking pan. In a large bowl, whisk together the flour, oats, baking soda, and salt. This helps distribute the leavening evenly and ensures that the oats won’t clump up. I find whisking the dry ingredients really smooths the mixing process later on.

Step 2: Cream Butter, Peanut Butter & Sugars

Using a stand mixer or handheld one, cream the room temperature butter, creamy peanut butter, and both sugars together on medium speed until light and fluffy — this usually takes about 2 minutes. Don’t forget to scrape down the bowl once or twice to make sure it’s fully combined. If you skip this, you might get pockets of sugar or peanut butter, which I don’t recommend!

Step 3: Add Eggs and Vanilla

Beat in the eggs one at a time, then add the vanilla extract. Mixing these in gradually helps prevent your batter from curdling or separating, which can affect how your bars bake up.

Step 4: Combine Wet & Dry Ingredients

Slowly add the dry ingredients to the wet mixture and stir until everything is just combined. Here’s what I’ve learned: try not to overmix at this point because it can make the bars tough. Stop mixing as soon as you no longer see flour.

Step 5: Stir in Chocolate Chips and M&M’s

Fold in the semi-sweet chocolate chips and one cup of M&M’s gently but thoroughly. This step brings all the fun and color to your bars, so don’t skimp out on the mix-ins!

Step 6: Spread Batter and Add Remaining M&M’s

Use a spatula to evenly spread the mixture into your greased pan. Then sprinkle the remaining half cup of M&M’s on top — this adds a beautiful colorful finish and a little extra crunch once baked.

Step 7: Bake and Finish with Sea Salt

Bake for 25-35 minutes, keeping an eye out for lightly golden brown edges and a set center. Be careful not to overbake — once the bars start to get dry, they lose that chewy magic. When you pull them from the oven, sprinkle flaky sea salt over the top right away; this salty contrast is what takes the bars to the next level. Allow them to cool completely before slicing into squares.

How to Serve Monster Cookie Bars Recipe

Garnishes

I always finish these bars off with a sprinkle of flaky sea salt right after baking—it really brings out the peanut butter and chocolate flavors. If you want to get festive, you can add a drizzle of melted peanut butter or a light dusting of powdered sugar. I’ve also tried adding a few extra M&M’s for a colorful pop just before serving, and it’s always a hit.

Side Dishes

These bars are perfect on their own, but I like pairing them with a cold glass of milk or a scoop of vanilla ice cream for an extra special treat. For a party, I often serve mini Monster Cookie Bars alongside fresh fruit to balance out the sweetness.

Creative Ways to Present

For birthdays or potlucks, I cut them into small bite-sized squares and arrange them on a colorful platter with some fresh flowers around the edges. Another idea I love is stacking a few bars on top of one another with little dollops of peanut butter frosting between layers for a tribute to classic layered desserts. It’s always a showstopper!

Make Ahead and Storage

Storing Leftovers

I keep leftover Monster Cookie Bars stored in an airtight container at room temperature. They stay deliciously chewy for up to 5 days. If you prefer them a bit softer, pop them in a sealed container with a slice of bread; the moisture gets absorbed into the bars and keeps them fresh longer.

Freezing

These bars freeze beautifully! I usually slice them into individual bars and wrap each bar tightly in plastic wrap, then place them in a freezer-safe bag. They last up to 3 months in the freezer, so you can have a stash of Monster Cookie Bars ready whenever you need a quick sweet fix.

Reheating

To reheat, I like to microwave a bar for about 15-20 seconds to revive the gooeyness, especially the chocolate chips. Alternatively, a quick 5-minute warm-up in a preheated 325°F oven works well if you want to refresh multiple bars. Just keep an eye on them to avoid drying out.

FAQs

Final Thoughts

I absolutely love how this Monster Cookie Bars Recipe brings together so many nostalgic flavors and textures in one slice — it’s like the ultimate cookie hybrid, but easier to share and slice. Every time I make these, friends and family can’t get enough, and honestly, I don’t blame them! If you’re looking for a cookie bar recipe that’s reliable, delicious, and slightly addictive, do yourself a favor and give this one a try. I promise it’ll become a staple in your baking rotation just like it did in mine.

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