If you’ve ever made my Quickie Monster Bars, this Halloween version will be our new fall favorite. These Halloween Monster Cookie Bars are chewy, peanut buttery, and loaded with candy-coated chocolate pieces, chocolate chips, and spooky Halloween sprinkles. Think of them as the playful, holiday cousin of your favorite monster cookie – ready to party in your favorite sprinkles.

Halloween Monster Cookie Bars are a super easy treat for kids with a halloween twist for fun!

Whether you’re making treats for a Halloween classroom party, a fall bake sale, or just need a dessert that screams “fun,” this recipe has you covered. The best part? You mix everything in one bowl, spread it into a pan, and bake – no chilling, no scooping, no mess.

Can you really get any more Halloween than when your snack is staring back at you?

Table of Contents

Why You’ll Love These Halloween Monster Cookie Bars

If you’re like me, you don’t always have the time or patience to make individual cookies when fall is in full swing and harvest season is calling your name. These bars are fast, foolproof, and full of flavor and fun.

Here’s why they’re a win:

Quick and easy: Just one bowl and no mixer required.
Loaded with goodies: M&M’s, mini chocolate chips, and spooky sprinkles make every bite festive.
Perfect for parties: Cut into squares and serve a crowd.
Make-ahead friendly: They stay soft and chewy for days, making them ideal for planning ahead.

These cookie bars are sweet, soft in the middle, and just the right amount of chewy – a mash-up between a peanut butter cookie and an oatmeal bar with extra Halloween flair.

Gather Your Ingredients

Here’s what you’ll need to make a pan of Halloween Monster Cookie Bars. If you love sweets like me, you probably already have most of this in your pantry and your sprinkle collection!

Ingredients

1/2 cup butter, softened
1 cup sugar
1 cup brown sugar, packed
1 cup creamy peanut butter
3 eggs
1 teaspoon vanilla extract
2 teaspoons baking soda
4 1/2 cups long-cooking oats, uncooked
1 cup candy coated chocolate pieces (like M&M’s)
3/4 cup mini semi-sweet chocolate chips
Halloween sprinkles, like skulls, bones, and candy eyes

Let’s make Halloween Monster Cookie Bars

These bars are so easy to whip up that you can have them cooling on the counter in less than an hour. Here’s the step-by-step breakdown:

Preheat your oven.
Set your oven to 350º and lightly spray a 15×10-inch jelly-roll pan or a large cookie sheet with non-stick spray. (You can also line the pan with parchment paper for easy removal and cleanup.)
Cream the butter and sugars.
In a large mixing bowl, beat together the softened butter, granulated sugar, and brown sugar until smooth and creamy.
Add the peanut butter and eggs.
Mix in the creamy peanut butter, eggs, and vanilla extract until well combined and smooth.
Incorporate baking soda.
Add the baking soda to the wet ingredients and stir to distribute evenly – this keeps the bars soft and slightly chewy.
Mix in the oats.
Stir in the uncooked oats until the batter is thick and evenly mixed. (It will look a little rough, and that’s okay – oats are what give these bars their hearty, chewy texture.)
Fold in the candy and chocolate chips.
Gently stir in the M&M’s and mini chocolate chips. Save a few for sprinkling on top later.
Spread the batter.
Press the cookie dough mixture evenly into your prepared pan. It’s thick, so use a spatula or your hands (lightly greased if needed) to spread it out to the edges.
Bake and decorate.
Place the pan in the oven and bake for 15 minutes. Carefully remove from the oven and sprinkle your Halloween sprinkles and candy eyes evenly over the top. This timing keeps your decorations from melting into the batter.
Return to the oven and bake for another 5 minutes, or until the edges are lightly golden and the center looks set.
Cool completely.
Allow the bars to cool in the pan before cutting. Once cooled, slice into squares or rectangles and serve.

Tips and Tricks for Perfect Monster Cookie Bars

Don’t overbake.
The trick to chewy cookie bars is pulling them out when they still look slightly underdone in the center. They’ll firm up as they cool.

Customize your candy.
Swap the M&M’s for Reese’s Pieces for more peanut butter flavor, or use seasonal candies for other holidays – Christmas, Valentine’s, Easter – this recipe works year-round!

No peanut butter?
You can substitute almond butter or sunflower butter if there’s a peanut allergy to consider. The texture may be a bit different, but they’ll still be delicious and festive.

Make ahead and store.
Store your bars in an airtight container at room temperature for up to 5 days. They also freeze beautifully – wrap tightly and store for up to 2 months.

How To Serve Halloween Monster Cookie Bars

These bars are festive on their own, but if you want to go the extra mile:

Serve with a scoop of vanilla ice cream and a drizzle of chocolate syrup.
Stack a few bars, wrap in collophane, and tie with Halloween ribbon for party favors.
Break them into chunks and mix into Halloween ice cream sundaes ro milkshakes.

They’re a fun and easy dessert for Halloween parties, classroom treats, or tailgate snacks during harvest season.

They don’t last long and all that is left are some eyes staring back at you!