Christmas Cookie Bars with Vanilla Frosting

When the butter and sugar turn pale and fluffy in the bowl, this dough starts out looking like a very simple sugar cookie. That simplicity is what I want here: Christmas Cookie Bars have the soft, familiar taste of a frosted sugar cookie, but the dough goes into one pan instead of being portioned cookie by cookie. I bake it as one slab, then finish the cooled surface with vanilla frosting and red-and-green sprinkles. The result is a batch of 24 bars with a smooth, festive top.

The powdered-sugar frosting is thick enough to stay on the bars but still smooth to spread. Each square has a soft crumb under a creamy finish, with a little crunch from the sprinkles. They’re a nice choice when you want a decorated holiday treat without shaping individual cookies.

Christmas Cookie Bars frosted with sprinkles

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Kitchen Note

Scatter the sprinkles as soon as the frosting is spread, while its surface is still soft. They’ll stick where they land instead of rolling off once the frosting starts to set.

Save these Christmas Cookie Bars for a holiday cookie tray: soft sugar-cookie centers, vanilla frosting, and a red-and-green sprinkle finish.

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Why an Even Layer Matters More Than a Deeply Golden Top

With a pan of cookie bars, the dough’s thickness decides how evenly the edges and center bake. If it’s piled higher in the middle, that part needs longer in the oven while the thinner edges keep baking. Pressing the dough into one even layer helps the whole slab finish at about the same time, so the center doesn’t stay doughy while the corners turn dry.

It’s also worth using the 9×13-inch pan for this amount of dough. A smaller pan makes a thicker slab, and a larger one makes a thinner slab; either change affects how quickly the bars bake. The doneness cue is intentionally modest: lightly golden edges and a center that looks set. Waiting for the whole surface to become deeply golden can take the softness out of the finished bars.

Once the dough is spread evenly, the oven does the work of turning it into a sturdy base for frosting. That makes the pan itself part of the texture, not just a place to hold the dough.

What Gives These Bars Their Soft Crumb and Smooth Frosting

Unsalted butter — Butter brings richness to both the bars and the frosting. Using unsalted butter lets the measured salt do its job in each part of the recipe; standard grocery-store butter is a good fit, so there’s no need for a specialty brand. Let it soften before mixing so it can beat smoothly.
Granulated sugar — This sugar creams with the butter to build the base of the bars. Keep it as granulated sugar rather than swapping in brown sugar, which would change the dough’s moisture and baked texture.
Large eggs — Eggs bind the dough and help it bake into a sliceable slab. Use large eggs for the intended balance of moisture and structure.
All-purpose flour and baking powder — All-purpose flour gives the bars enough structure to hold frosting and cut cleanly, while baking powder provides lift. Ordinary all-purpose flour works well here; no specialty flour is needed.
Powdered sugar — Its fine texture is what makes the frosting smooth. Granulated sugar won’t dissolve the same way in this butter frosting, so powdered sugar is the right choice.
Whole milk, vanilla, and sprinkles — Whole milk helps bring the frosting to a spreadable consistency, and vanilla flavors both the frosting and the bars. Red-and-green holiday sprinkles add the familiar decorated finish; their main job is color and a little crunch.

From Creamed Butter to a Frosted Slab

Cream the Butter and Sugar Until Fluffy

Heat the oven to 350°F and grease a 9×13-inch baking pan. Beat the softened butter and granulated sugar in a large bowl for about 2 minutes, until the mixture looks light and fluffy rather than dense. Beat in the eggs and vanilla until they’re combined. Butter that’s still cold won’t cream as smoothly, so start with softened butter.

Mix the Dry Ingredients Just Until Combined

Whisk the flour, baking powder, and salt together in a separate bowl so the leavening is evenly distributed. Add that mixture to the butter mixture and mix only until no dry flour remains. The dough will be thick, not pourable. Press it evenly into the prepared pan, paying attention to the corners so they aren’t thinner than the center.

Bake Until the Center Looks Set

Bake for 20 to 24 minutes. Look for lightly golden edges and a center that appears set; the top doesn’t need to become deeply browned. If the edges are already getting dark, the bars are baking past the point where they’ll stay soft. Cool the bars completely in the pan before adding frosting, or the butter in the topping will soften and slide.

Spread the Frosting and Finish the Top

Beat the softened frosting butter until smooth, then beat in the powdered sugar and salt. Add the vanilla and whole milk, then beat until the frosting is smooth and spreadable. Spread it evenly over the completely cooled bars and scatter the sprinkles over the top. Once the frosting has set, cut the slab into 24 bars.

Two Easy Ways to Change the Cut

Make Bite-Size Party Squares

Cut the frosted slab into 48 smaller pieces instead of 24 bars. You’ll have a more petite treat for a dessert table, though each piece will have less of the soft cookie base and frosting in every bite.

Cut Cookie-Swap Fingers

Slice the slab into long, narrow rectangles rather than square bars. The ingredients and bake stay the same, but the slimmer shape is easy to arrange in rows on a cookie platter.

Storage and Reheating

Refrigerator: Store in an airtight container for up to 4 days. The frosting firms and the bars feel denser when cold.
Freezer: Freeze cut bars in a single layer until firm, then transfer them to an airtight container with parchment between layers. They keep well for up to 2 months; thaw in the refrigerator.
Reheating: These are best served without reheating. Let refrigerated bars sit at room temperature for about 20 minutes before serving; microwaving can soften the frosting unevenly.

Questions That Come Up When Making Christmas Cookie Bars

Can I use salted butter instead of unsalted butter?+

You can, but the bars and frosting will taste saltier because each already includes salt. For the intended balance, use unsalted butter in both parts.

Can I bake these in a different size pan?+

The 9×13-inch pan gives this amount of dough the intended thickness. A smaller or larger pan changes how quickly the center and edges bake, so use the listed pan for the most even result.

Can I use a stand mixer for the dough and frosting?+

Yes. A stand mixer works for both, as does a hand mixer; use the same texture cues and stop mixing the dough once the flour disappears. The mixer type doesn’t change the ingredients or baking time.

How do I transport the bars without smudging the frosting?+

Let the frosting set before packing the bars in a flat, covered container. If you need to stack them, separate the layers with parchment so the decorated tops don’t press against one another.