Funfetti Cookie Bars

These Funfetti Cookie Bars are the ultimate easy dessert recipe made with Funfetti cake mix, crushed Oreos, and colorful M&M’s. Soft, chewy, festive, and packed with birthday cake flavor, they’re perfect for everything from summer parties and bake sales to birthdays and holiday celebrations.

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If there’s one thing I can never resist, it’s a shortcut dessert that tastes like you spent way more time making it than you actually did. That’s exactly what happened with these Funfetti Cookie Bars.

I started with a box of Patriotic Funfetti Cake Mix I had sitting in my pantry and turned it into the most irresistible cookie bars loaded with crushed Oreos and M&M’s. The result? A thick, chewy dessert that’s part cookie, part blondie, and completely impossible to stop eating.

What I love most about this recipe is how customizable it is. I used the patriotic version of Funfetti cake mix because I was making these for a summer gathering, but you can use any Funfetti cake mix throughout the year and switch up the colors of the M&M’s to match birthdays, holidays, school parties, or special occasions.

Whether you’re looking for an easy Fourth of July dessert, a colorful birthday treat, or just something fun to bake with the kids, these Funfetti Cookie Bars always disappear fast.

Why You’ll Love This Recipe

These cookie bars are one of those desserts that checks every box.

• Made with just a few simple ingredients
• Starts with a box cake mix shortcut
• Soft and chewy texture
• Loaded with Oreos and M&M’s
• Perfect for birthdays and celebrations
• Easy enough for beginner bakers
• Great make-ahead dessert
• Customizable for any holiday
• Ready in about 30 minutes

Ingredients

A few simple ingredients come together to make these festive cookie bars.

• Patriotic Funfetti Cake Mix – I used the patriotic version with red, white, and blue sprinkles, but any Funfetti cake mix works perfectly.
• Eggs – Help bind the dough together and create a chewy texture.
• Vegetable Oil – Keeps the bars soft, moist, and tender.
• Oreo Cookies – Crushed and mixed into the dough for cookies-and-cream flavor.
• M&M’s – Add color, crunch, and chocolate in every bite.

How to Make Funfetti Cookie Bars

These couldn’t be easier to make.

Step 1: Prepare the Pan

Preheat your oven to 350°F.

Line an 8×8-inch baking dish with parchment paper or lightly grease the pan.

Step 2: Make the Dough

In a large mixing bowl, combine the Funfetti cake mix, eggs, and vegetable oil.

Mix until a thick cookie dough forms.

Step 3: Add the Mix-Ins

Fold in most of the crushed Oreos and M&M’s, reserving a handful of M&M’s for topping after baking.

Step 4: Bake

Press the dough evenly into the prepared baking dish.

Sprinkle additional crushed Oreos over the top.

Bake for 22-28 minutes, or until the edges are lightly golden and the center is just set.

Step 5: Decorate

Remove from the oven and immediately sprinkle additional M&M’s over the top while the bars are still warm.

Allow the bars to cool before slicing.

Watch How to Make It

Variations

One of the best things about these Funfetti Cookie Bars is how easy they are to customize for different holidays, parties, and occasions. Simply swap the cake mix, candies, or mix-ins to create a completely new dessert.

• Birthday Cake Funfetti Cookie Bars – Add extra rainbow sprinkles and use rainbow-colored M&M’s for the ultimate birthday dessert.
• Fourth of July Funfetti Cookie Bars – Use Patriotic Funfetti Cake Mix and red, white, and blue M&M’s for an easy patriotic dessert recipe.
• Cookies and Cream Funfetti Cookie Bars – Double the crushed Oreos for even more cookies-and-cream flavor in every bite.
• Chocolate Funfetti Cookie Bars – Swap the Funfetti cake mix for chocolate cake mix and use chocolate M&M’s.
• Holiday Funfetti Cookie Bars – Change the M&M colors to match Christmas, Easter, Halloween, Valentine’s Day, or any holiday celebration.
• Peanut Butter Cookie Bars – Use peanut butter M&M’s for a sweet and salty twist.

Expert Tips for the Best Funfetti Cookie Bars

These simple baking tips will help ensure your Funfetti Cookie Bars turn out soft, chewy, and bakery-worthy every time.

• Do not overbake the cookie bars. The center should still look slightly soft when you remove them from the oven. They will continue to set as they cool.
• Use room temperature eggs for the smoothest dough and most even texture.
• Reserve some M&M’s for the top. Pressing additional M&M’s onto the bars immediately after baking gives them that bakery-style appearance.
• Line your baking dish with parchment paper. This makes removing and slicing the bars much easier.
• Leave the Oreo cookies slightly chunky. Larger Oreo pieces create the best texture and pockets of cookies-and-cream flavor.
• Allow the bars to cool completely before slicing. This helps the bars hold their shape and creates cleaner squares.
• Use any Funfetti cake mix flavor. While I used Patriotic Funfetti Cake Mix, this recipe works with any seasonal or classic Funfetti cake mix variety.

Make-Ahead, Storage, and Freezing Instructions

One of the best things about these Funfetti Cookie Bars is that they’re perfect for making ahead. In fact, I think they’re even better the next day once the flavors have had time to settle and the bars become extra soft and chewy.

Make Ahead

If you’re making these Funfetti Cookie Bars for a birthday party, holiday gathering, bake sale, or school celebration, you can bake them up to 2 days in advance. Once completely cooled, cover the baking dish tightly with plastic wrap or transfer the bars to an airtight container.

For the freshest presentation, wait to add any extra M&M’s on top until the day you’re serving them.

How to Store Funfetti Cookie Bars

Store leftover cookie bars in an airtight container at room temperature for up to 5 days. Keeping them tightly covered helps maintain their soft and chewy texture.

If stacking the bars, place a sheet of parchment paper between layers to prevent them from sticking together.

Can You Refrigerate Cookie Bars?

You can refrigerate these bars if needed, but it’s not necessary. Refrigeration may cause them to firm up slightly. If chilled, allow them to sit at room temperature for 15-20 minutes before serving for the best texture.

How to Freeze Funfetti Cookie Bars

These cake mix cookie bars freeze beautifully, making them a great make-ahead dessert for busy weeks and holiday baking.

To freeze, allow the bars to cool completely before slicing. Wrap individual bars in plastic wrap and place them in a freezer-safe container or zip-top freezer bag. Freeze for up to 3 months.

When ready to enjoy, thaw at room temperature for about 30 minutes or overnight in the refrigerator.

Frequently Asked Questions

Can I use a different cake mix?

Yes! Any Funfetti cake mix works. You can also experiment with yellow, white, chocolate, or strawberry cake mix.

Can I use mini M&M’s?

Absolutely. Mini M&M’s work great and distribute evenly throughout the bars.

Can I use Double Stuf Oreos?

Yes. Double Stuf Oreos add even more cookies-and-cream flavor.

How do I know when they’re done?

The edges should be lightly golden and the center should be set but still soft. Avoid overbaking.

Can I double the recipe?

Yes. Double the ingredients and bake in a 9×13-inch pan.

You’ll Also Love

If you love easy dessert bars, patriotic treats, and crowd-pleasing cookie recipes, here are a few more reader favorites to try next:

• Patriotic Magic Cookie Bars – Loaded with festive red, white, and blue candies, these easy dessert bars are perfect for summer parties and holiday celebrations.
• Mini S’mores Skillet Cookies – Individual-sized s’mores cookies topped with marshmallows and ice cream for the ultimate summer dessert.
• S’mores Cookies – Soft, chewy cookies packed with graham crackers, chocolate, and gooey marshmallows.
• Patriotic Berry Trifle – A beautiful red, white, and blue layered dessert that’s always a hit at Fourth of July cookouts and summer gatherings.