Name: Frosted Sugar Cookie Bars
Prep time: 15 min
Cook time: 23 min
Total time: 105 min
Ingredients: 1 1/2 cups all-purpose flour, spooned and leveled; 1/2 teaspoon baking powder; 1/4 teaspoon baking soda; 1/4 teaspoon cream of tartar; 6 tablespoons salted butter (softened to room temperature); 3/4 cup granulated sugar; 1/2 teaspoon Diamond Crystal kosher salt (or 1/4 teaspoon fine salt); 1 large egg plus 1 large egg yolk; 2 teaspoons pure vanilla extract; 2/3 cup Easter M&Ms, (divided); Sprinkles, (optional); 1/4 cup unsalted butter, softened to room temperature; 1 1/4 cups powdered sugar; 1 tablespoon heavy cream; 3/4 teaspoon pure vanilla extract; Pinch of salt; Gel food coloring, (optional)

Frosted sugar cookie bars are the cheat code for when you want homemade sugar cookies but don’t have time to roll, cut, and bake 47 individual rounds. I tested two versions of this recipe: a higher-butter ratio that came out flat, and a leaner build with cream of tartar that finally nailed the chewy, bakery-style bite I was after.

A batch of square sugar cookie bars topped with bright pink frosting, pastel-colored candy-coated chocolates, and sprinkles, arranged on a white surface. One bar is pulled slightly away from the group.

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My first version used more butter and came out flat, soft, but no chew. I rebuilt the recipe with a leaner butter-to-sugar ratio and cream of tartar, which gave these the chewy, structured bite you get from a good bakery sugar cookie. The base is adapted from Sarah Kieffer’s method because her ratios just work, and I built the M&M-and-frosting situation on top.

If you are on an Easter baking run, my Cinnamon Toast Crunch Marshmallow Treats are another no-fuss crowd-pleaser the kids can help make start to finish. And for something with real visual impact on a dessert table, my Fruity Pebbles Cupcakes bring the same pastel rainbow energy. And if you want something a little more indulgent on that tray, my Brown Butter Mini Egg Blondies bring the same Cadbury mini egg energy with a fudgy, caramel-like base.

Why You’ll Love This Recipe

One-pan simplicity – No rolling pin, no cookie cutters, no dough chilling. Just press into an 8×8 pan and bake.
Bakery-style texture – Cream of tartar is the secret. It gives these bars that soft, chewy bite you’d expect from a fancy bakery sugar cookie.
Fun and colorful – Easter M&Ms make these feel festive, but you can swap in any M&M variety for year-round baking.
Make-ahead friendly – Bake the bars up to 24 hours ahead and frost the day you’re serving them. Perfect for party prep.
Kid-approved – Soft, sweet, and loaded with candy. These disappear fast at our house, just like my chocolate chip rice krispie treats when I put them out for after-school snacks.

Frosted Sugar Cookie Bars

Top-down view of separated baking ingredients on a marble surface.

For the Sugar Cookie Bars:

All-purpose flour — Weigh it if you can. If measuring by volume, spoon the flour into the cup and level with a straight edge. Never scoop directly from the bag, which packs in extra flour and is the most common reason these come out dry.
Cream of tartar — Do not skip this one. It works with baking soda to create that chewy, slightly tangy bakery-sugar-cookie crumb. This is what makes the texture of this recipe different from that of a standard soft bar.
Salted butter — I switched to salted butter for cookies after the New York Times started using it in their cookies and haven’t looked back; it kicks the flavor up in a way unsalted just doesn’t. I kept the added salt in the recipe too, and the bars are better for it.
Granulated sugar — The higher sugar-to-butter ratio is intentional. It is what gives this recipe its chewy texture. Do not reduce it.
Diamond Crystal kosher salt — If you are using fine table salt or Morton’s, use half the amount. Diamond Crystal is less dense, and you need twice the volume to get the same saltiness.
Egg plus egg yolk — The extra yolk adds richness and keeps the bars moist even with the leaner butter amount.
Easter M&Ms — For folding into the dough and sprinkling on top. Use regular-sized M&Ms. You need about 2/3 cup total — 1/3 cup in the dough and 1/3 cup on top. One standard 10-oz bag covers both, with some left over.

For the Buttercream Frosting: You will need butter, powdered sugar, vanilla, heavy cream, salt, and food coloring if desired. For food coloring, I like gel colors made from Americolor.

See recipe card below for exact quantities.

Substitutions and Variations

Store-bought frosting: Betty Crocker Rich and Creamy Vanilla Frosting works well on these. It is soft enough to spread without warming, takes gel food coloring, and sets up reasonably. However, homemade buttercream is better!
Make it for any holiday: Same recipe, different M&M colors. Red and pink for Valentine’s Day, red and green for Christmas, red, white, and blue for the Fourth of July, or any mix for birthdays.
Add sprinkles: Sprinkles work great. Use jimmies (the long tube-shaped ones) rather than nonpareils, which bleed color into light frosting as they sit.
Cream cheese frosting: Would give a tangier, less-sweet frosting.
Skip the M&Ms in the dough: If you just want the topping version, leave the 1/3 cup out of the dough.

This recipe has not been tested with other substitutions or variations. If you replace or add any ingredients, please let us know how it turned out in the comments below!

How to Make Frosted Sugar Cookie Bars

Small, pale yellow butter granules clumped together in a clear mixing bowl, with a ring-shaped gap in the center showing the bottom of the bowl.

Beat the butter on medium speed until smooth, about 1 minute. Add the sugar and salt and beat until combined. The mixture will look sandy and dry. That is correct.

A close-up of a glass mixing bowl filled with creamy, yellow cake batter, showing a smooth and slightly textured consistency.

Mix in the egg, egg yolk, and vanilla extract, then beat on medium speed for about 1 minute, until the dough is smooth. Scrape down the sides of the bowl.

A hand holding a spatula mixes cookie dough with colorful candy-coated chocolates in a clear glass bowl.

Add the flour mixture and mix on low until just combined, stop the second you no longer see dry streaks. Fold in 1/3 cup Easter M&Ms with a spatula; a few gentle folds are all it takes.

A hand with dark red nail polish presses cookie dough with colorful candy-coated chocolate pieces into a baking pan.

Drop the dough in small spoonfuls across the pan, then press into an even layer. The dough is quite sticky and a little tricky to spread evenly. Spray a little oil on your hands or use an offset spatula to help get it into the corners.

A square baking pan lined with parchment paper contains a large, golden-brown cookie bar with colorful candy pieces visible on the surface. The pan sits on a marble countertop.

Bake for 20 to 25 minutes, until the edges are golden and the center looks just set and matte but still pale.

A close-up of a hand holding a black electric mixer blending bright pink frosting or batter in a mixing bowl. The swirled mixture looks creamy and thick.

Beat the butter until smooth, then mix in the powdered sugar, vanilla, heavy cream, and salt. Tint with a toothpick tip of gel food coloring. Beat on medium-high for 2 to 3 minutes until fluffy.

A rectangular sugar cookie with smooth, bright pink frosting spread evenly on top, photographed on a light marble surface.

Lift the cooled bars out using the parchment overhang. Spread frosting over the completely cooled bars.

A square cookie with pink frosting, topped with pastel-colored candy-coated chocolates and round sprinkles, displayed on a white surface.

Immediately sprinkle the remaining 1/3 cup Easter M&Ms into the frosting. Let the frosting set for 15 minutes, and cut into squares.

Sarah’s Tips

Do not try to cream the butter and sugar into a fluffy stage. This recipe does not have enough butter for that. Beat the butter alone first until smooth, then add the sugar. The mixture will look sandy, that is correct. The eggs are what smooth everything out in the next step.
Use a scale if you can. 177 grams of flour is the exact tested amount. If you measure by volume, spoon the flour into the cup and level it, scooping from the bag packs in extra flour and is the most common reason these come out dry.
Do not skip the cream of tartar. It is not a fancy ingredient it is in the spice aisle right next to the baking powder. It is what gives these bars that chewy, slightly tangy bakery sugar cookie bite. Without it you get a soft bar. With it you get a chewy one.
Pull the bars when the center still looks pale. Golden edges, set and matte center, pale throughout. The bars will firm up as they cool in the hot pan. Waiting until they look done in the oven means they are already overdone.
Fold M&Ms in gently. A few passes with a spatula is all it takes. The mixer will crack the shells and you will end up with tie-dye dough.
Why did my bars turn out dry and cakey? Too much flour is the most likely cause. Use a scale or spoon-and-level. Overbaking is the second most likely cause. Pull them at the pale, just-set stage even if the center feels slightly underdone.
Why did my frosting slide off? The bars were not fully cooled. Even bars that feel cool on top can still be warm in the center. Give them 45 to 60 minutes, or put them in the fridge for 20 minutes if you are in a hurry.

FAQs

Yes, and this is the smartest way to handle Easter morning. Bake the bars the night before, cool completely, wrap the pan tightly, and leave at room temperature. Make and spread the frosting the next day. The bars are actually a little better on day two, everything settles and the texture evens out.

Sprinkles work great, use jimmies (the long tube-shaped ones) rather than nonpareils, which bleed color into light frosting as they sit. Mini chocolate chips are another easy swap. Or just skip the topping entirely and go frosting-only. The bar is good on its own.

This recipe is sized for an 8×8 pan. For a 9×13 crowd-sized batch, roughly double the cookie base and frosting

The candy shells protect the chocolate, so they do not fully melt, they hold their shape but soften slightly and the shells crack a little on top.

It matters a little. A light-colored metal pan gives the most even bake, which is what this recipe is tested on. Glass retains heat and cooks the edges faster than the center. If glass is all you have, reduce oven temperature by 25 degrees F and start checking a few minutes early.

Yes, but the bars will be thinner and will bake faster. Start checking at 18 minutes instead of 20.

Storage

Room temperature: Store in an airtight container for up to 2 days. If you are stacking them, layer parchment between layers so the frosting does not stick.

Refrigerator: Up to 5 days. The frosting firms up in the cold; set them out for 20 to 30 minutes before serving, and it softens back up.

Make-ahead: You can bake the bars and make the frosting up to 1 day ahead. Store the covered bars at room temperature and the covered frosting in the fridge. Frost before cutting and serving.

Freezing: Unfrosted bars freeze well for up to 3 months. Thaw overnight in the fridge, then frost, cut, and serve.