These festive cookie bars bring together buttery brown-sugar cookie dough, chocolate chips, and colorful M&M’s in one easy-to-bake dessert. You can make them thick and chewy in a 9 × 13-inch pan or thinner in a 15 × 10-inch pan, then finish them with extra candies and chocolate chips for an eye-catching holiday treat.

Ingredients

• 1 cup unsalted butter, softened to room temperature
• 1 cup light brown sugar
• 3/4 cup granulated sugar
• 2 large eggs
• 2 teaspoons vanilla extract
• 3 cups all-purpose flour
• 1 teaspoon baking soda
• 1 teaspoon salt
• 1 cup chocolate chips, plus extra for the top if desired
• 1 cup M&M’s, plus extra for the top if desired

Instructions

1. Prepare the Oven and Pan: Preheat your oven to 325°F. For thicker cookie bars, line a 9 × 13-inch baking pan with foil. If you prefer thinner bars, use a 15 × 10-inch pan instead. Leave some foil extending beyond the edges of the pan to make removing the finished bars easier. Lightly coat the lined pan with nonstick cooking spray.
2. Cream the Butter and Sugars: Add the softened butter, light brown sugar, and granulated sugar to a large mixing bowl. Using an electric mixer, beat them together for about 1 minute until combined and creamy.
3. Add the Eggs and Vanilla: Add the eggs and vanilla extract to the butter mixture. Continue mixing until everything is well incorporated.
4. Make the Cookie Dough: Add the flour, baking soda, and salt. Stir just until the dry ingredients are incorporated into the wet mixture. Avoid overmixing. Gently fold in the chocolate chips and M&M’s, reserving about 1/4 cup of the candies and chocolate chips for decorating the top.
5. Transfer to the Pan: Scoop the prepared cookie dough into the lined and greased baking pan. Spread it out evenly across the pan. Scatter the reserved M&M’s and additional chocolate chips over the surface.
6. Bake: Place the pan in the preheated oven and bake for 30 to 35 minutes. The cookie bars are ready when the top is just lightly golden brown.
7. Cool and Slice: Let the baked cookie bars cool completely before lifting them out of the pan using the foil overhang. Once fully cooled, cut them into individual bars.
8. Store: Keep the cookie bars in an airtight container for up to 3 days.