This holiday traybake has been a centerpiece of my December baking for years: soft, buttery cookie bars loaded with chocolate chips and festive red, green, and white M&Ms. I first created this version during a chaotic December when I needed a crowd-pleasing treat that traveled well and didn’t require decorating individual cookies. The result was exactly what I wanted — the tender chew of a perfectly baked cookie, the snap of candy-coated chocolate, and a glossy top dotted with bright holiday colors. Every year neighbors and friends ask when I’ll be bringing these to the cookie swap, and the recipe has become my go-to for school parties and office treats.

What makes these bars special is how forgiving they are: the batter is easy to mix by hand or with a mixer, and the pan method means uniform slices and consistent baking. The combination of granulated and brown sugar gives depth of flavor and chew, while a modest amount of butter keeps them rich without being greasy. The final touch of extra candies pressed on top before baking creates an irresistible, professional-looking finish. Make them ahead, slice them into neat squares, and watch how quickly they disappear at any holiday gathering.

Ingredients

• Unsalted butter (1 cup): Use room-temperature butter for proper creaming. European-style butter (82–85% fat) gives a slightly richer flavor; if using salted butter, reduce added salt.
• Granulated sugar (1 cup): Adds sweetness and helps with spreading; use regular white sugar for the classic texture.
• Brown sugar, packed (1 cup): Light brown sugar adds moisture and that caramel-like depth essential for chewy bars; pack into the cup for an accurate measure.
• Large eggs (2): Bring eggs to room temperature for better emulsion and structure; they bind the batter and provide lift.
• Vanilla extract (2 teaspoons): Use pure vanilla for best flavor; imitation vanilla works in a pinch but won’t be as deep.
• All-purpose flour (2 3/4 cups): Spoon and level for accuracy; this provides the structure without making the bars cakey.
• Baking soda (1 teaspoon): Gives a modest lift and helps create the soft crumb.
• Salt (1/2 teaspoon): Balances sweetness — essential even when using salted butter, though reduce if your butter is heavily salted.
• Chocolate chips (1 cup): Semisweet or milk chocolate chips add pockets of melted chocolate; mini chips distribute more evenly if you prefer consistency.
• Holiday-colored chocolate candies (1–1 1/2 cups): Use red, green, and white M&Ms for a festive look; reserve a small handful to press on top before baking.
• Optional extras: A pinch of cinnamon or 1/2 cup chopped toasted pecans or walnuts for warmth and crunch.

Instructions

Step 1 — Prepare the pan and oven: Preheat the oven to 350°F (177°C). Line a 9x13-inch baking pan with parchment paper, leaving an overhang for easy removal, or grease the pan with butter and lightly flour it. This ensures clean edges and easy lifting when cool. Step 2 — Cream butter and sugars: In a large bowl, beat 1 cup softened unsalted butter with 1 cup granulated sugar and 1 cup packed brown sugar using a handheld mixer or stand mixer on medium speed until light, pale, and fluffy — about 2–3 minutes. Scrape the bowl once to incorporate all sugar. Proper creaming traps air that helps create a tender crumb. Step 3 — Add eggs and vanilla: Beat in 2 large eggs, one at a time, followed by 2 teaspoons vanilla extract. Mix until fully incorporated but avoid overbeating; you want a smooth, glossy batter, not a foam. Step 4 — Combine dry ingredients: Whisk together 2 3/4 cups all-purpose flour, 1 teaspoon baking soda, and 1/2 teaspoon salt in a separate bowl. Add the dry mix to the wet ingredients in two additions, mixing on low until just combined. Overmixing develops gluten and can make bars tough. Step 5 — Fold in chocolate and candies: Fold in 1 cup chocolate chips and 1–1 1/2 cups holiday M&Ms with a spatula, reserving 2–3 tablespoons of candies to press on top. Folding gently preserves the batter’s aeration and prevents the candies from cracking. Step 6 — Spread and decorate: Transfer the batter into the prepared pan and spread it evenly with an offset spatula. Sprinkle the reserved candies on top and press gently — this gives a colorful, glossy finish after baking. Step 7 — Bake and test for doneness: Bake at 350°F (177°C) for 18–22 minutes, rotating halfway through. The center should be set but still slightly soft; edges will be golden. A toothpick inserted near the center should have a few moist crumbs but not wet batter. Overbaking dries out the bars. Step 8 — Cool and slice: Cool in the pan on a wire rack for at least 30 minutes, then lift out using the parchment overhang and slice into 24 bars. For clean slices, chill briefly and use a sharp knife wiped between cuts.

Storage Tips

Store cooled bars in an airtight container layered with parchment to prevent sticking. At room temperature they keep well for 48 hours; for longer storage refrigerate up to 5 days. For freezing, tightly wrap the cooled pan-cut bars in plastic wrap and then foil, or place in a single layer in a freezer container for up to 3 months. Thaw overnight in the refrigerator or at room temperature for a few hours. To refresh slightly stale bars, warm in a 300°F oven for 5–7 minutes — the candies will regain a slight sheen.

Ingredient Substitutions

If you need to swap ingredients, use the following ratios and expect slight texture changes: replace half the butter with vegetable shortening for a slightly more cake-like texture; swap up to 1/2 cup of all-purpose flour with almond flour for nutty depth (note: this will affect structure); use gluten-free 1-to-1 flour blend if avoiding gluten but do not expect identical chew; and substitute equal amounts of white chocolate chips or peanut butter chips for chocolate chips for flavor variety. For egg-free, use 2 commercial egg replacers or 1/2 cup unsweetened applesauce plus 1 tablespoon ground flax mixed with 3 tablespoons water, though texture will be denser.

Serving Suggestions

Serve slices on a festive platter lined with parchment and garnished with a few extra candies and a sprig of rosemary for holiday contrast. Pair with hot cocoa, mulled cider, or coffee for an afternoon treat. For gift boxes, layer bars between wax paper and tie with ribbon. Cut bars into smaller squares for cookie exchanges or into larger rectangles for portable lunchbox treats. They also make a cheerful addition to dessert tables alongside shortbread and peppermint bark.

Cultural Background

While candy-studded cookie bars don’t have a single origin story, they reflect a long-standing American tradition of pan-baked sweets that prioritize convenience and shareability at communal gatherings. The M&M candy itself debuted in the 1940s and quickly became a popular mix-in for baking in later decades. Combining cookie dough with colorful candies became especially popular during holiday seasons when bright, festive colors are desired. These bars are a modern holiday adaptation of classic chocolate chip cookie flavors presented in a form that’s easy to portion and transport.

Seasonal Adaptations

Adapt these bars for seasons and celebrations by switching the candy colors and mix-ins: autumn harvest bars with orange and brown candies plus chopped toasted pecans; Valentine’s Day bars with pink and red candies and white chocolate chips; or patriotic summer bars using red, white, and blue candies. Incorporate seasonal spices — a pinch of ground ginger and cinnamon for winter warmth or citrus zest and chopped dried cranberries for a bright, festive twist.

Meal Prep Tips

For make-ahead convenience, bake and cool the entire pan, then slice and store individual portions in small containers or freezer bags. Label with date and contents. When packing lunches, place a bar in a small resealable bag with a piece of parchment to prevent sticking. If preparing for a large event, scale the recipe and bake in multiple pans, or double the batter and bake in two pans simultaneously if your oven allows. Keep presentation simple by stacking squares and tying with twine for easy gifting.

These Christmas M&M cookie bars are an effortless, joyful addition to any holiday spread. They bake quickly, travel well, and bring a smile to faces of all ages — try a batch this season and make it your new tradition.