The edges of these cookie bars turn lightly golden before the center looks fully baked, and that’s the moment I watch rather than waiting for a deep color. In a 9×13-inch pan, the dough bakes into one even slab that’s easy to lift, cut, and decorate; there’s no rolling pin or cookie cutters to wrestle with. These Christmas Tree Sugar Cookie Bars give you the buttery bite of a sugar cookie in a simple bar, with a piped green tree on every piece.
The dough is soft enough to press into the pan, but sturdy enough to hold its shape once baked and cooled. I keep the flour measurement careful and mix only until the dry patches disappear, which keeps the bars tender instead of tough. Then the green frosting goes into a zip-top bag for quick zigzags, and each tree gets its own sprinkle finish and yellow star. The finished bars are festive without needing a fussy decorating setup.
Kitchen Note
Snip just a small corner off the zip-top bag; a wide opening makes the frosting hard to control on these narrow bars. If the zigzags look uneven at first, keep your hand moving steadily from side to side and finish each tree with its star.
Save these Christmas Tree Sugar Cookie Bars for a festive bake with tender centers, green frosting trees, and a star on every bar.
Why These Bars Should Come Out Before the Edges Get Deeply Brown
Sugar cookies are easy to overbake because the edges give you the first obvious sign of color. For bars, that can be misleading: a deeply browned edge usually means the outer pieces will be firmer than the center. I look for lightly golden edges and a center that appears set, then let the slab cool completely in the pan. That balance gives you a bar that holds together when cut without turning crisp all the way through.
The pan shape does some of the work here. Rather than baking individual cookies with different amounts of spread, you press the dough into one even layer, so the bars bake together and are easy to portion. Keeping that layer level matters more than packing the dough down hard. If one area is much thicker than another, it can finish baking at a different pace, and you’ll lose the soft, consistent bite that makes these bars worth making.
Why the Butter, Egg Yolk, and Gel Color Matter in These Tree Bars
- Unsalted butter — Butter gives the bars their rich, tender crumb and forms the base of the frosting. Standard unsalted butter works well; there’s no need for a specialty brand. Softened butter creams smoothly with the sugar, while cold butter won’t beat to the same light texture. I’d stick with butter rather than swapping in margarine, since the bars and frosting both depend on its texture.
- Egg and egg yolk — The whole egg binds the dough, and the extra yolk adds richness that helps keep the bars tender. Room-temperature eggs blend more evenly into the creamed butter. Leaving out the yolk changes the texture, so I don’t recommend that swap for this batch.
- All-purpose flour — Spoon it into the measuring cup and level it off rather than scooping directly from the bag. Scooping can pack in too much flour, making the dough harder to press and the baked bars dry. All-purpose flour gives the bars enough structure to cut cleanly while keeping a soft cookie texture.
- Powdered sugar and gel food coloring — Powdered sugar makes a smooth frosting that can be piped, while gel coloring gives it a clear green shade without adding much liquid. The whole milk loosens the mixture, so add the powdered sugar gradually and judge the final texture by whether it holds a pipeable zigzag. Gel coloring is the better choice here than liquid coloring, which can make the frosting too loose.
- Vanilla extract — Vanilla rounds out both the cookie dough and the frosting. The recipe uses it in each, so measure the two portions separately before mixing; it’s easy to forget that the frosting needs its own teaspoon.
From Soft Dough to Piped Christmas Tree Decorations
Cream the Butter and Sugar Until Fluffy
Beat the softened butter with the granulated sugar for about 2 minutes, until the mixture looks lighter and fluffy. Scrape the bowl if butter is clinging to the sides so the egg can mix in evenly. Add the egg, egg yolk, and vanilla for the bars, then beat just until combined. If the mixture looks a little uneven after the eggs go in, keep mixing only until it comes together.
Mix the Dough Without Overworking It
Whisk the flour, baking powder, and salt in a separate bowl so the leavening is distributed through the flour. Add the dry mixture to the butter mixture and mix just until no dry patches remain. The dough will be thick, not pourable, and that’s what lets it hold a neat bar shape. Mixing beyond that point can make the finished cookie bars tougher.
Press, Bake, and Cool the Slab
Heat the oven to 350°F and line a 9×13-inch pan with parchment, leaving enough overhang to lift out the cooled bars. Press the dough into an even layer, reaching the corners without leaving a thicker mound in the middle. Bake for 20 to 24 minutes, until the edges are lightly golden and the center looks set. Cool the cookie completely in the pan before lifting it out with the parchment and cutting it into 12 bars.
Pipe the Trees While the Frosting Is Smooth
Beat the remaining butter with the powdered sugar, vanilla, milk, and green gel coloring, adding the sugar gradually until the frosting is smooth and pipeable. Transfer it to a zip-top bag and snip a small corner. Pipe a zigzag tree onto each cooled bar, then add the Christmas sprinkles and a yellow star-shaped sprinkle while the frosting is fresh. If the frosting won’t hold its shape, it’s too loose for neat trees; the gradual addition of sugar helps you reach a texture that pipes cleanly.
Two Simple Ways to Change the Look of These Sugar Cookie Bars
Make White Vanilla Trees
Leave out the green gel coloring and pipe the vanilla frosting as white zigzag trees. The flavor stays the same, while the green and yellow sprinkles stand out more against the pale frosting.
Use a Gluten-Free Baking Blend
For a gluten-free version, replace the all-purpose flour with the same volume of a cup-for-cup gluten-free baking blend made for baking. The bars may be a little more delicate when cut, so let the slab cool completely before lifting it from the pan.
Storage and Reheating
- Refrigerator: Keep the decorated bars in an airtight container for up to 4 days. The frosting firms up when chilled, and the cookie texture is softer after the bars sit briefly at room temperature.
- Freezer: Freeze the unfrosted bars in an airtight container for up to 2 months, with parchment between layers. Thaw them in the refrigerator, then decorate once they’re thawed.
- Reheating: These bars don’t need 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 Decorating Christmas Tree Bars
Christmas Tree Sugar Cookie Bars
Ingredients
Equipment
Method
- Heat the oven to 350°F.
- Line a 9x13-inch baking pan with parchment paper, leaving enough overhang to lift out the bars.
- In a large bowl, beat 1 cup of the butter with the granulated sugar until light and fluffy, about 2 minutes.
- Beat in the egg, egg yolk, and 1 teaspoon of the vanilla until combined.
- In a separate bowl, whisk together the flour, baking powder, and salt.
- Mix the dry ingredients into the butter mixture just until no dry patches remain.
- Press the dough evenly into the prepared pan.
- Bake for 20 to 24 minutes, until the edges are lightly golden and the center looks set.
- Cool completely in the pan.
- Lift the cooled cookie from the pan using the parchment.
- Cut it into 12 bars.
- Beat the remaining 1/2 cup butter with the powdered sugar, remaining 1 teaspoon vanilla, milk, and green food coloring, adding the sugar gradually, until smooth and pipeable.
- Transfer the frosting to a zip-top bag and snip off a small corner.
- Pipe a zigzag tree shape onto each bar.
- Decorate each tree with Christmas sprinkles.
- Top each tree with a yellow star-shaped sprinkle.
