Copycat Costco Blueberry Muffins

This copycat Costco muffin recipe makes jumbo, bakery-worthy blueberry muffins with a tall domed top and a buttery streusel crunch. They come together in one bowl with simple ingredients, and the texture stays moist for days.

If you’ve ever wanted to recreate those huge muffins from the warehouse store at home, this recipe gets you there without a trip. Even the first time, the batter is forgiving and the tops rise exactly how you hope they will.

What Makes These Muffins So Good

I’ve worked through a lot of muffin recipes, and this one sticks because it nails the tall, crackly top without any fussy steps. Buttermilk and oil keep the crumb tender and soft, and the batter is thick enough to hold big pockets of blueberry.

A short blast of high heat right at the start pushes the tops into that signature dome, and the streusel adds a buttery, cinnamon-scented crunch on every bite. You can swap the blueberries for raspberries or chocolate chips without changing the method at all.

Ingredients

• 2 1/2 cups all-purpose flour: spooned and leveled, not scooped, to avoid a dry muffin.
• 1 1/4 cups granulated sugar: regular white sugar gives a clean sweetness.
• 2 tsp baking powder: check the date so it’s still active.
• 1/2 tsp baking soda: helps the muffins brown and rise.
• 1/2 tsp fine salt: balances the sweetness.
• 1 cup buttermilk: full-fat or low-fat both work.
• 1/2 cup vegetable oil: neutral oil keeps the crumb moist longer than butter.
• 2 large eggs: room-temperature eggs blend more smoothly.
• 1 tsp vanilla extract: use the real stuff if you have it.
• 2 cups fresh or frozen blueberries: if using frozen, do not thaw first.
• 1 tbsp all-purpose flour: for tossing with the blueberries so they don’t sink.

For the streusel topping:

• 1/4 cup all-purpose flour
• 1/4 cup packed light brown sugar
• 2 tbsp unsalted butter, melted
• Pinch of ground cinnamon

A Few Swaps You Can Make

• Frozen blueberries: toss them in 1 tbsp of flour straight from the freezer. Do not thaw them first or the batter will turn purple.
• Raspberries or blackberries: use the same amount; fold gently so the berries don’t break apart.
• Chocolate chip muffins: swap the blueberries for 1 1/2 cups semisweet chocolate chips and skip the streusel if you prefer.
• Lemon zest: add 1 tsp finely grated zest to the wet ingredients for a bright lift.
• Dairy-free: replace buttermilk with 1 cup unsweetened almond milk mixed with 1 tbsp lemon juice; let it sit 5 minutes before using.

Smoothie King Angel Food Smoothie goes great with these muffins when you want something to sip.

How to Make Copycat Costco Blueberry Muffins

Step 1: Whisk the Dry Ingredients

Preheat your oven to 375°F (190°C) and line a 6-cup jumbo muffin pan with paper liners. In a large bowl, whisk together the 2 1/2 cups flour, 1 1/4 cups sugar, baking powder, baking soda, and salt until everything looks evenly distributed.

The mixture will look fluffy and uniform, with no streaks of baking powder or soda. A quick, thorough whisk now saves you from dense patches in the finished muffins.

Step 2: Beat the Wet Ingredients

In a medium bowl, whisk the buttermilk, vegetable oil, eggs, and vanilla together until the eggs are fully broken down and the mixture is smooth, about 1 minute. No streaks of yolk should remain.

The buttermilk gives a subtle tang that keeps the sweetness in check. If your buttermilk is cold take it out of the fridge 10 minutes before you start, the batter will come together more evenly.

Step 3: Fill the Muffin Cups and Top

Pour the wet mixture into the dry ingredients and fold with a flexible spatula until only a few streaks of flour are visible. Toss the blueberries with 1 tbsp of flour, then add them to the bowl and fold just until they’re scattered through the batter, about 8 to 10 strokes. Divide the thick batter among the 6 jumbo cups, filling each one nearly to the top.

In a small bowl, mix the streusel flour, brown sugar, melted butter, and cinnamon with a fork until crumbly. Sprinkle about 1 heaping tablespoon over each muffin, covering the batter completely. The crumbly bits will bake into a crunchy golden cap.

Step 4: Bake the Muffins

Slide the pan into the oven and immediately increase the temperature to 400°F (200°C). Bake for 5 minutes, then drop the heat back to 375°F (190°C) and continue baking until the tops are deep golden and a toothpick poked into the center of a muffin comes out clean, about 20 to 25 minutes more.

The muffins will dome dramatically in those first few minutes. If the tops brown too quickly, loosely tent the pan with foil. Rotate the pan halfway through the bake time so the color is even.

Step 5: Cool the Muffins and Serve

Let the muffins cool in the pan on a wire rack for 5 minutes. Then gently lift them out by the liners and transfer to the rack to cool completely, or serve them warm if you can’t wait.

The paper peels away easily once the muffins are no longer steaming hot. Warm muffins with bursting blueberries and a crunchy top are hard to beat, but they also slice neatly at room temperature.

Tips for Tall, Bakery-Size Tops

• Start with room-temperature ingredients.: Cold eggs or buttermilk can make the batter stiff and the rise less dramatic. Let them sit on the counter for 20 minutes.
• Fill the cups all the way.: Jumbo muffin liners should be nearly full. The batter needs that height to push upward and form a dome.
• No jumbo pan?: Use a standard 12-cup muffin tin instead. Fill each cup about 3/4 full (the recipe will yield closer to 12) and start checking for doneness around 18 minutes.
• The high-heat start is the trick.: That blast of 400°F at the beginning causes the batter to puff fast and set the shape before the interior finishes baking. Don’t skip it.

Bake times after the initial 400°F blast:

Keeping Leftover Muffins Fresh

• Refrigerate:: Store cooled muffins in an airtight container in the fridge for up to 4 days.
• Freeze:: Wrap each muffin individually in plastic wrap, then place in a zip-top bag and freeze for up to 2 months.
• Reheating:: Microwave a refrigerated muffin for 20 to 30 seconds, or heat a frozen one for about 1 minute, until warm.

Frequently Asked Questions

Can I make these muffins dairy-free?

Yes. Replace the buttermilk with 1 cup unsweetened almond milk mixed with 1 tbsp lemon juice, and use a neutral oil for the streusel butter. The texture stays close to the original.

What if I want to add lemon zest?

Add 1 tsp finely grated lemon zest to the wet ingredients. It brightens the blueberry flavor without making the batter watery.

Why did my streusel sink into the muffins?

That usually happens when the batter is too thin or the streusel pieces are large and heavy. Make sure to fold the batter just until combined, keep it thick, and break the streusel into small crumbles before sprinkling.

Can I double the recipe?

Yes. Double all the ingredients and divide the batter between two jumbo pans. Bake one pan at a time so the heat circulates well.

Costco Blueberry Muffins Recipe

Print Recipe Pin Recipe

Prep Time 15 minutes mins

Cook Time 28 minutes mins

Total Time 43 minutes mins

Servings: 6 servings

Calories: 480

Ingredients Method Notes

Ingredients

  

• 2 1/2 cups all-purpose flour
• 1 1/4 cups granulated sugar
• 2 tsp baking powder
• 1/2 tsp baking soda
• 1/2 tsp fine salt
• 1 cup buttermilk
• 1/2 cup vegetable oil
• 2 large eggs
• 1 tsp vanilla extract
• 2 cups fresh or frozen blueberries
• 1 tbsp all-purpose flour (for tossing blueberries)
• 1/4 cup all-purpose flour (for streusel)
• 1/4 cup packed light brown sugar
• 2 tbsp unsalted butter, melted
• Pinch of ground cinnamon

Method

 

1. Preheat oven to 375°F, line a jumbo 6-cup muffin pan, and whisk together the 2 1/2 cups flour, sugar, baking powder, baking soda, and salt in a large bowl.
2. In a medium bowl, whisk buttermilk, oil, eggs, and vanilla until smooth.
3. Fold wet ingredients into dry until just combined, then toss blueberries with 1 tbsp flour and gently fold them in. Divide batter among the jumbo cups and sprinkle with streusel made from 1/4 cup flour, brown sugar, melted butter, and cinnamon.
4. Bake at 400°F for 5 minutes, then reduce to 375°F and bake 20 to 25 minutes until golden and a toothpick comes out clean.
5. Cool in the pan 5 minutes, then transfer to a rack. Serve warm or at room temperature.

Notes

If you don’t have buttermilk, stir 1 tbsp lemon juice into 1 cup milk and rest 5 minutes. The batter is thick on purpose, so don’t thin it. For the tallest muffins, stick with the high-heat start. Frozen blueberries work straight from the freezer, no thawing needed.