This pan of Christmas cookie bars is my go-to for holiday gatherings and last-minute cookie swaps. I first made these during a hectic December when I wanted something faster than individual cookies but with the same classic cookie taste and chewy texture. The result is a buttery, slightly crisp-edged bar loaded with semi-sweet chocolate chips and festive red-and-green M&M’s that hold their color and add joyful crunch. It’s the kind of sweet that fills the kitchen with warm sugar-and-butter aromas and invites everyone to grab a napkin and a second (or third) square.

I discovered this combination after adapting a favorite chocolate chip cookie into a traybake: by keeping the dough slightly thicker and pressing it into a 9×13-inch pan, you get bars that bake evenly and slice cleanly. The white chocolate chips scattered on top add a sweet contrast to the semi-sweet chips inside, while the brown sugar gives a subtle caramel note and chewy crumb. This version is especially great for cookie exchanges because it travels well, slices neatly, and the festive candies make it look special without extra decorating time.

Ingredients

• Butter (¾ cup / 1½ sticks): Use unsalted butter at room temperature for easy creaming. I like Plugrá or Kerrygold for a rich flavor; if you only have salted butter, reduce added salt slightly.
• Vanilla extract (2 teaspoons): Real vanilla extract gives deep aromatics. Pure vanilla improves the background flavor more than imitation.
• Granulated sugar (2/3 cup): Balances the brown sugar and helps create a slight crispness on the edges.
• Brown sugar (1 cup, packed): Adds moisture and a caramel note; light brown sugar works beautifully for chewiness.
• Eggs (2 large): Bring the mixture together and contribute structure — use room-temperature eggs to help with emulsification.
• All-purpose flour (3 cups): Measure accurately: spoon into the cup and level off rather than scooping, or use a kitchen scale (about 360 g if you weigh it).
• Baking soda (1 teaspoon) & Salt (1 teaspoon): Leaven and season the dough — salt heightens the chocolate flavor, so don’t skip it.
• Semi-sweet chocolate chips (1 cup): I recommend Nestlé or Ghirardelli for melt-and-bite texture; fold into the dough so they stay mostly intact.
• Christmas M&M’s (1 cup, divided): Use ½ cup folded into the dough and ½ cup sprinkled on top for color and texture contrast.
• White chocolate chips (¼ cup): Scatter on top for a sweet, creamy counterpoint to the semi-sweet chips below.

Instructions

Preheat and prepare the pan: Preheat your oven to 325°F. Lightly grease a 9×13-inch baking pan or line it with parchment paper leaving a collar for easy removal. An even layer and parchment will help you slice clean bars once cooled. Cream butter and sugars: In a large bowl, beat ¾ cup softened butter with 1 cup packed brown sugar and 2/3 cup granulated sugar on medium speed for about 3 minutes. Beat until the mixture is light, pale, and fluffy — this incorporates air and creates a tender crumb. Add eggs and vanilla: Beat in the 2 large eggs one at a time, followed by 2 teaspoons vanilla extract. Scrape the bowl’s sides occasionally so the mixture is smooth and homogenous; this helps with even texture in the finished bars. Combine dry ingredients: Mix together 3 cups all-purpose flour, 1 teaspoon baking soda, and 1 teaspoon salt in a separate bowl. Add the dry mixture gradually to the wet, mixing on low speed or with a spatula until just combined. Overmixing develops gluten and will make bars tough. Fold in mix-ins: Gently fold in 1 cup semi-sweet chocolate chips and ½ cup Christmas M&M’s using a spatula. Distribute the mix-ins so each bite will have chocolate and candy — avoid beating them in or they’ll break down. Press dough and add toppings: Spread the dough evenly into the prepared pan, using an offset spatula or lightly greased hands to smooth the surface. Sprinkle the remaining ½ cup M&M’s and ¼ cup white chocolate chips on top, pressing very lightly so they adhere but don’t sink. Bake and cool: Bake in the preheated oven for 26–30 minutes or until the edges are lightly golden and the center is set but still soft to the touch. Remove from the oven and allow the bars to cool completely in the pan before slicing — cooling prevents crumbling and helps set the interior.

Storage Tips

To store, cool the bars completely, then place them in an airtight container layered with parchment paper to prevent sticking. At room temperature they stay fresh for about 3–4 days; refrigeration extends shelf life to a week but can slightly firm the texture — allow bars to sit 20–30 minutes at room temperature before serving. For longer storage freeze individual slices in a single layer on a baking sheet, then transfer to a freezer-safe bag or container for up to 3 months. Reheat frozen bars briefly in a warm oven (325°F for 8–10 minutes) or microwave a single serving for 10–20 seconds to restore softness.

Ingredient Substitutions

Want to adapt? Substitute equal parts gluten-free all-purpose flour if you need a wheat-free option — expect a slightly different crumb and slightly more fragility. For dairy-free, replace butter with a solid baking margarine (use a reliable brand like Earth Balance) and choose dairy-free chocolate chips; results will be similar though slightly less rich. Swap semi-sweet chips for dark chocolate for a more intense flavor, or use chopped baking chocolate for larger melty pockets. If you’d like nutty crunch, fold in ¾ cup chopped pecans or walnuts — toast them lightly first for deeper flavor.

Serving Suggestions

Serve warm with a scoop of vanilla ice cream or chilled with hot cocoa for a cozy pairing. For holiday platters, cut smaller 1.5-inch squares and arrange them with shortbread, peppermint bark, and spiced nuts for a colorful dessert board. Garnish individual servings with a dusting of powdered sugar or a light drizzle of melted white chocolate to emphasize the festive look. These bars also pair nicely with coffee or a rich eggnog for a classic seasonal spread.

Cultural Background

Traybakes and pan cookies have long been staples in American home baking because they deliver the same flavors as drop cookies but with speed and convenience. The idea of pressing cookie dough into pans can be traced to pragmatic home cooks who needed to feed crowds without the labor of portioning dozens of cookies. The addition of brightly colored candies for holidays is a modern twist that borrows from celebratory confection traditions — the M&M was introduced in the 1940s and quickly became a festive favorite for seasonal baking.

Seasonal Adaptations

Adapt this base for other holidays by swapping the candies and chips: use autumn-hued candy corn and chopped toasted pecans for Thanksgiving, pastel candies for Easter, or mini chocolate eggs for spring celebrations. For a winter twist, stir in ½ teaspoon ground cinnamon and ¼ teaspoon ground cardamom to the dough for warm spice notes. You can also replace the M&M’s with crushed peppermint candies and top with white chocolate for a peppermint bark-style bar perfect for Christmas morning.

Meal Prep Tips

For easy gifting, slice bars into uniform squares and layer them in shallow tins with parchment between layers. Label tins with baking date and storage instructions. To speed up assembly for multiple pans, mix the dry ingredients in one large bowl and wet ingredients in another, then combine and fold in mix-ins; refrigerate the dough for 15–20 minutes if it becomes too soft to spread. Pre-portioning the M&M’s into bowls and measuring chips ahead of time streamlines the process and reduces clean-up.

These Christmas cookie bars are simple, festive, and reliable — a recipe I return to every year because it delivers delicious results with minimal fuss. Try it once and you’ll see why it earns a permanent spot in the holiday rotation.