Monster Cookie Bars

There’s something magical about Monster Cookie Bars—they’re the kind of dessert that disappears before you can even grab a second one. Chewy from the oats, rich with peanut butter, and dotted with melty chocolate chips and bright candy-coated chocolates, they’re a total crowd-pleaser. I swear, every time I make a batch for friends, the tray is wiped clean in minutes.

These bars take me right back to baking with my little cousins during summer breaks. We’d fight over who got to sprinkle the extra M&M’s on top (I always let them win—mostly). The best part? No scooping or chilling required—just mix, spread, bake, and try not to eat half the pan straight from the oven. Trust me, it’s harder than it sounds.

Why You'll Love These Monster Cookie Bars

Listen, I know everyone claims their recipe is "the best," but these bars? They’re in a league of their own. Here’s why you’ll fall head over heels for them:

Chewy and Packed with Flavor

That perfect chew from the oats? Check. The way peanut butter and chocolate melt together in every bite? Double check. And those candy-coated chocolates? They add little bursts of sweetness that’ll make you reach for "just one more" (spoiler: it’s never just one).

Easy to Make

No fancy techniques here—just dump, mix, and bake. Seriously, you don’t even have to chill the dough! One bowl, ten minutes of prep, and you’re done. Even my nephew can make these without turning the kitchen into a disaster zone (mostly).

Crowd-Pleasing

Birthday party? Potluck? "I-need-a-sugar-fix" Tuesday? These bars work for everything. Kids go wild for the colorful candies, adults pretend they’re "just sampling" then sneak thirds, and lunchboxes magically come home empty. They’re like edible happiness in every square.

Ingredients for Monster Cookie Bars

Grab these pantry staples—you probably have most already! I swear by name-brand peanut butter here (the cheap stuff makes them grainy). And don’t skip the extra M&M’s for topping; they make the bars look bakery-worthy.

The Wet Stuff

• ½ cup unsalted butter, softened (leave it out for 30 minutes—no microwave cheating!)
• 1 cup packed brown sugar (pack it tight—this isn’t the time to be shy)
• ½ cup granulated sugar
• 1 cup creamy peanut butter (Jif or Skippy work best—natural separates too much)
• 2 large eggs (room temp helps them mix smoother)
• 1 teaspoon vanilla extract (the real stuff, please!)

The Dry Team

• 1 teaspoon baking soda
• ½ teaspoon salt (I use kosher—table salt is too harsh here)
• 2 cups old-fashioned oats (not instant—they turn to mush)
• 1 ½ cups all-purpose flour (scoop and level—no packing!)

The Fun Mix-Ins

• 1 cup semi-sweet chocolate chips (Guittard or Ghirardelli melt perfectly)
• 1 cup candy-coated chocolates (M&M’s or similar), plus extra for sprinkling

How to Make Monster Cookie Bars

Okay, let’s get baking! These bars come together so fast, you’ll be sneaking bites before the oven even finishes preheating. Just follow these simple steps—I promise it’s foolproof.

Prep the Dough

First, preheat your oven to 350°F (175°C) and grab that 9x13-inch pan. Grease it well—I use butter or nonstick spray, but parchment paper works too if you’re paranoid about sticking (no judgment).

Now, the fun part: in a big bowl, cream together the softened butter, brown sugar, and granulated sugar until it’s light and fluffy. This takes about 2 minutes with a hand mixer—don’t rush it! Then add the peanut butter, eggs, and vanilla. Mix until smooth, scraping down the sides so everything gets cozy.

Next, sprinkle in the baking soda and salt. Give it a quick mix, then gradually add the oats and flour. Stop when just combined—overmixing makes tough bars, and nobody wants that. Fold in the chocolate chips and candies gently with a spatula. The dough will be thick, like a cookie dough you could eat with a spoon (not that I’ve done that… often).

Bake to Perfection

Spread the dough evenly in your prepared pan—it’ll look like a lot, but trust me, it bakes up perfectly. Sprinkle those extra M&M’s on top like confetti (this is the best part—no skimping!).

Bake for 20-25 minutes until the edges turn golden brown but the center still looks slightly soft. They’ll keep cooking as they cool, so resist the urge to overbake! Let them cool completely in the pan—this is crucial for clean cuts. I know, waiting is torture, but hot bars crumble into sad pieces. Once cooled, slice into squares and watch them disappear.

Tips for the Best Monster Cookie Bars

After making roughly a million batches of these bars (okay, maybe dozens), I’ve learned all the tricks to bakery-quality results. Follow these tips and yours will turn out perfect every time—no magic required.

Avoid Overmixing

When you add the flour and oats, mix just until the streaks disappear. Overworked dough makes tough, dense bars instead of that dreamy chew we love. I stop my mixer early and finish by hand—it’s worth the extra 30 seconds of stirring!

Customize Your Mix-Ins

The beauty of these bars? You can riff on them endlessly. Swap semi-sweet chips for butterscotch or peanut butter ones, toss in chopped pretzels for salty crunch, or go wild with Reese’s Pieces instead of M&M’s. My neighbor adds shredded coconut, and honestly? Game changer.

Watch the Clock

The edges should be golden but the center still slightly jiggly when you pull them out—they’ll set as they cool. Overbaking is the #1 reason bars turn from chewy to hockey pucks. Set a timer for 20 minutes and start checking.

Storing and Freezing Monster Cookie Bars

Here’s the good news: these bars stay delicious for days! Keep them in an airtight container at room temperature—they’ll stay fresh and chewy for up to 5 days (if they last that long). For longer storage, freeze them in a single layer before stacking with parchment paper between layers. They’ll keep for 3 months, but let’s be real—you’ll eat them way before then.

Monster Cookie Bars FAQs

Got questions? I’ve got answers! Here’s everything you need to know to make these bars absolutely perfect—no guesswork required.

Can I Use Natural Peanut Butter?

Honestly? I wouldn’t recommend it. Natural peanut butter separates and makes the bars oily. Stick with regular creamy peanut butter (like Jif or Skippy) for that perfect texture. If you must use natural, drain off any excess oil first and add an extra tablespoon of flour to compensate.

How Do I Keep Them Chewy?

The secret’s in the storage! Once cooled, tuck them into an airtight container with a slice of bread—sounds weird, but the bread keeps them soft for days. Just swap the bread when it gets hard. Also, underbake slightly (like I mentioned earlier)—that gooey center firms up to ideal chewiness as they cool.

Can I Make These Without Eggs?

Yep! For each egg, mix 1 tablespoon ground flaxseed with 3 tablespoons water, let it sit for 5 minutes until gel-like, then use as directed. They’ll be slightly denser but still delicious. My vegan sister swears by this hack!

Nutritional Information

Nutritional values are estimates and vary by ingredients/brands. Per bar: ~220 calories, 10g fat, 28g carbs, 5g protein. Enjoy responsibly—or not!

Share Your Creation!

I'd love to see your monster cookie bars in action! Snap a photo of your gorgeous creation and tag me—I live for those melty chocolate-and-candy shots. Leave a rating or comment below if you try this recipe, and don’t forget to brag about how fast they disappeared in your house (we’ve all been there). Happy baking!

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