This Copycat Costco Vanilla Sheet Cake is the kind of simple, crowd-pleasing dessert that shows up at potlucks, birthdays, and last-minute celebrations. It’s tender, super-vanilla, and frosts into a smooth, nostalgic finish—easy enough for weeknight baking but impressive enough for company. If you love easy copycat recipes that turn dinner guests into fans, try this other savory favorite on the site: Chick-fil-A crispy chicken sandwich copycat.
Why you’ll love this dish
This sheet cake nails the classic Costco vibe: a thin, even crumb with a rich, buttery vanilla frosting that’s not too sweet. It’s inexpensive to make (pantry staples), fast to pull together, and scales easily when you need to serve a crowd. Parents appreciate that kids will eat it without complaint, hosts like that it transports well, and bakers like that the technique is forgiving.
“I made this for a last-minute work potluck—everyone asked for the recipe. Soft, buttery, and exactly like the cake you get from the bakery.” — home baker review
How this recipe comes together
The process is straightforward: whisk the dry ingredients, cut softened butter into the flour/sugar mix until crumbly (this creates a tender crumb), then add eggs and vanilla for structure and flavor. Milk thins the batter so it bakes into an even sheet. After 25–30 minutes in a 9×13-inch pan, cool completely before frosting. The frosting is a simple buttercream—beat butter until creamy, add sifted powdered sugar gradually, then thin with a splash of heavy cream if needed.
What you’ll need
- 2 cups all-purpose flour
- 1 1/2 cups granulated sugar
- 1 tablespoon baking powder
- 1/2 teaspoon salt
- 1 cup (2 sticks) unsalted butter, softened (for cake)
- 4 large eggs, room temperature
- 1 tablespoon vanilla extract
- 1 cup whole milk
For the frosting:
- 4 cups powdered sugar, sifted if lumpy
- 1/2 cup (1 stick) unsalted butter, softened
- 1 teaspoon vanilla extract
- 1/4 cup heavy cream (optional — to adjust consistency)
Notes: Room-temperature eggs and butter give the best emulsion and even texture. Whole milk yields the richest crumb, but 2% or a buttermilk swap (for tang) also works.
Step-by-step instructions
- Preheat oven to 350°F (175°C). Grease and lightly flour a 9×13-inch sheet pan, or line it with parchment leaving an overhang for easy removal.
- In a large bowl, whisk together 2 cups flour, 1 1/2 cups granulated sugar, 1 tablespoon baking powder, and 1/2 teaspoon salt until evenly combined.
- Add 1 cup softened butter to the dry mix. Use a pastry cutter, fork, or your fingertips to work the butter in until the mixture resembles coarse crumbs. This method mimics the tender crumb of the Costco cake.
- Add eggs one at a time, mixing after each addition so the batter becomes smooth and cohesive. Stir in 1 tablespoon vanilla extract.
- Pour in 1 cup whole milk and mix until the batter is smooth and pourable—scrape the bowl so everything is incorporated. Batter should be thick but spreadable.
- Spread batter evenly into the prepared pan and smooth the top. Bake 25–30 minutes, rotating halfway if your oven runs hot. A toothpick inserted in the center should come out with a few moist crumbs, not raw batter.
- Remove from oven and let cool completely in the pan on a wire rack before frosting to prevent the frosting from sliding.
Frosting:
- Beat 1/2 cup softened butter until creamy, about 1–2 minutes on medium speed.
- Gradually add 4 cups powdered sugar, mixing on low until combined, then on medium until smooth.
- Add 1 teaspoon vanilla extract. If frosting is too stiff, add up to 1/4 cup heavy cream, one tablespoon at a time, until spreadable. If too thin, add a little more powdered sugar.
- Spread evenly on the cooled cake with an offset spatula. Decorate as desired.
Best ways to enjoy it
Serve chilled or at room temperature. This cake pairs beautifully with:
- A tall mug of coffee or a milky latte for breakfast or brunch.
- A scoop of vanilla bean ice cream for an indulgent dessert.
- Fresh berries or a berry compote spooned on the side for a bright contrast.
- Simple piping and colorful sprinkles for birthdays or school events.
Slicing tip: use a long, sharp knife and wipe it between cuts for clean edges.
Storage and reheating tips
- Room temperature: Store covered tightly at room temperature for 1–2 days (buttercream will be fine).
- Refrigerator: Keep in an airtight container or covered pan for up to 5–7 days; let come to room temperature before serving for best texture.
- Freezing: Wrap individual slices or the whole cake (well-wrapped in plastic, then foil) and freeze for up to 3 months. Thaw in the refrigerator overnight, then bring to room temperature before serving.
- Reheating: If you prefer warm cake, microwave a single slice for 10–15 seconds (watch closely so frosting doesn’t melt). There’s no need to reheat the entire sheet.
Food safety: because the cake is baked and eggs are cooked, it’s safe when fully baked; don’t keep at ambient room temperature beyond recommended times if you live in hot climates.
Pro chef tips
- Use room-temperature ingredients: eggs and butter at room temp incorporate more easily and give a smoother batter.
- Don’t overmix: once the milk is added and the batter is smooth, stop mixing—overworking develops gluten and makes the cake dense.
- Butter technique: working butter into the dry mix creates a slightly coarser crumb that mimics store-bought sheet cakes—try it rather than creaming for this recipe.
- Sift powdered sugar for a silky frosting and add cream gradually to control the consistency.
- For ultra-smooth frosting, press a piece of plastic wrap directly onto the frosted surface and chill 15 minutes, then smooth with a warm offset spatula.
- If you’re exploring other copycat kitchen projects for holidays or parties, you might also like the savory sandwich recreation on the site: copycat Chick-fil-A crispy chicken sandwich.
Creative twists
- Lemon-vanilla: Add 1 tablespoon lemon zest to the batter and 1–2 teaspoons lemon juice to the frosting.
- Strawberry sandwich cake: Split the cooled sheet horizontally, spread a thin layer of jam and fresh sliced strawberries, then frost.
- Chocolate swirl: Fold 1/3 cup cocoa powder mixed with 2–3 tablespoons milk into a portion of batter and swirl before baking.
- Browned-butter frosting: Brown the frosting butter for nutty depth, cool, then proceed with powdered sugar.
- Dietary swaps: Use oil (3/4 cup) and an extra egg for a moister crumb, or try dairy-free butter and coconut milk for a vegan-friendly version (result will differ slightly).
Common questions
Q: How long does this cake take from start to finish?
A: Active prep is 15–20 minutes; baking is 25–30 minutes; cooling and frosting add at least 30–60 minutes depending on how cool you let it get. Plan roughly 1.5–2 hours total if you want it fully set before serving.
Q: Can I make this in advance?
A: Yes. Bake the cake a day ahead, wrap tightly, and frost the next day for freshest presentation. You can also freeze unfrosted layers and frost after thawing.
Q: What if my frosting is too runny or too stiff?
A: Too runny: add more powdered sugar, 1/4 cup at a time. Too stiff: add heavy cream or milk, one teaspoon at a time, until spreadable.
Q: Can I double this recipe?
A: Yes—use two 9×13 pans or a larger sheet pan and increase bake time slightly; check doneness with a toothpick. For very large pans, bake in batches for even results.
Q: Is this exactly Costco’s recipe?
A: This is a copycat inspired by the flavor and texture of Costco’s vanilla sheet cake. It reproduces the key characteristics—tender crumb and smooth buttercream—but Costco’s exact commercial recipe and methods are proprietary.
If you want clarification on any step, substitutions for dietary needs, or help scaling the recipe, ask and I’ll walk you through it.
Print
Copycat Costco Vanilla Sheet Cake
- Prep Time: 20 minutes
- Cook Time: 30 minutes
- Total Time: 60 minutes
- Yield: 16 servings
- Category: Dessert
- Method: Baking
- Cuisine: American
- Diet: Vegetarian
Description
A tender, super-vanilla sheet cake with rich, buttery frosting inspired by Costco’s famous dessert.
Ingredients
- 2 cups all-purpose flour
- 1 1/2 cups granulated sugar
- 1 tablespoon baking powder
- 1/2 teaspoon salt
- 1 cup (2 sticks) unsalted butter, softened (for cake)
- 4 large eggs, room temperature
- 1 tablespoon vanilla extract
- 1 cup whole milk
- 4 cups powdered sugar, sifted if lumpy (for frosting)
- 1/2 cup (1 stick) unsalted butter, softened (for frosting)
- 1 teaspoon vanilla extract (for frosting)
- 1/4 cup heavy cream (optional — to adjust frosting consistency)
Instructions
- Preheat oven to 350°F (175°C). Grease and lightly flour a 9×13-inch sheet pan or line it with parchment.
- In a large bowl, whisk together flour, sugar, baking powder, and salt.
- Add softened butter to the dry mix and work it in until the mixture resembles coarse crumbs.
- Add eggs one at a time, mixing after each addition until smooth. Stir in vanilla extract.
- Pour in whole milk and mix until smooth and pourable.
- Spread batter evenly into the prepared pan and smooth the top. Bake for 25–30 minutes, rotating halfway, until a toothpick comes out with moist crumbs.
- Let cool completely in the pan on a wire rack before frosting.
- For the frosting, beat softened butter until creamy. Gradually add powdered sugar and mix until smooth, then add vanilla extract. Adjust consistency with heavy cream as needed.
- Spread frosting evenly on the cooled cake and decorate as desired.
Notes
Room-temperature ingredients yield the best texture. Cake pairs well with coffee or fresh berries.