Peanut Butter Cookie Bars with M&M’s: Chewy Chocolate Candy Bars

Soft, chewy cookie bars packed with peanut butter flavor, studded with M&M’s and semisweet chocolate chips. This easy, crowd-pleasing recipe comes together quickly and makes a colorful, irresistible treat for any occasion.

These M&M Peanut Butter Cookie Bars are a favorite for good reason.

The texture is soft and chewy with a rich peanut butter base, and the candies add pops of color and crunch throughout each bar.

What makes this recipe so appealing is how simple it is: no chilling required and straightforward mixing means you can have a pan in the oven in minutes.

Because the recipe yields a large batch, it’s perfect for sharing at parties, bake sales, or family gatherings.

Ingredients For This Peanut Butter Cookie Bar Recipe

• Unsalted butter – softened but still cool (about 1 1/2 sticks / 3/4 cup). This texture helps make the bars dense and fudgy.
• Smooth peanut butter – standard creamy peanut butter works well; crunchy is fine if you prefer texture.
• Brown sugar (dark or light) – pack the cup firmly when measuring.
• Granulated sugar – balances the brown sugar for texture and sweetness.
• Large egg + 1 egg yolk – this combo keeps the bars fudgy and chewy.
• Vanilla extract – adds depth of flavor.
• All-purpose flour – spoon and level when measuring to avoid a dry, heavy result.
• Baking powder and baking soda – for proper rise and texture.
• Coarse kosher salt – if using fine table salt, halve the amount called for.
• M&M’s – standard or seasonal colors to suit the occasion.
• Semisweet chocolate chips – complement the peanut butter and balance the candy’s sweetness.

How To Make M&M Cookie Bars

Preheat the oven to 350°F (175°C).

Line a 13 x 9-inch pan with two pieces of aluminum foil, crossing them in the center so you have an overhang to lift the bars out later. Grease the foil with cooking spray or butter and set aside.

In a mixer (stand or hand), beat the butter until smooth. Add the peanut butter and beat until light and fluffy.

Add the brown and granulated sugars and beat until the mixture is well combined and slightly lighter in color. Scrape down the bowl with a rubber spatula.

Add the whole egg, egg yolk, and vanilla; mix until just blended.

With the mixer on low, add the flour, baking soda, baking powder, and salt. Mix until the flour is almost incorporated — it’s okay to see a few streaks of flour.

Fold in the M&M’s and semisweet chocolate chips gently by hand until evenly distributed. Avoid overmixing.

Press the dough evenly into the prepared 13 x 9-inch pan. Bake at 350°F for about 22 minutes, until the edges are lightly browned and puffed and the center is just set.

Cool completely at room temperature. When cooled, lift the bars from the pan using the foil overhangs, remove the foil, trim the edges if desired, and cut into 24 squares.

Pro Tips

Follow these tips to ensure soft, chewy bars:

1. Don’t overmix. Stop mixing the flour in while you can still see streaks; finish combining when you fold in the candies.
2. Fold in the M&M’s and chocolate chips by hand to keep them intact and avoid overworking the dough.
3. Slightly underbake — remove the pan when the center is just set to preserve a soft, chewy texture and account for carryover cooking while cooling.

Storing Your Peanut Butter Cookie Bars

Store the bars in an airtight container at room temperature for up to one week. To extend shelf life, refrigerate in an airtight container or wrapped tightly in plastic wrap.

Can I Freeze These Bars?

Yes — these bars freeze very well. I often freeze extras because the recipe yields a lot. Thaw in the refrigerator until soft enough to enjoy, or let thaw completely at room temperature if you prefer.

Variations and Customizations

Customize the bars to suit holidays or taste preferences:

• Use seasonal M&M colors (orange and black for Halloween, red and green for Christmas, pink and red for Valentine’s Day).
• Swap in peanut M&M’s or peanut-butter-filled M&M’s for extra peanut flavor.
• Use peanut butter chips instead of semisweet chocolate chips for a more uniform peanut profile.

Some Other Sweet Treats You May Enjoy:

• Golden Grahams S’mores Bars
• Perfect Cheesecake Squares
• Chocolate Covered Popcorn
• From Scratch Birthday Cake Cookies
• Frosted Sugar Cookie Bars