Jumbo Lemon Blueberry Costco Muffins Recipe

Giant muffins are moist and tender, loaded with beautiful floral flavor from vanilla and sweet blueberries, and elevated with refreshing lemon zest.

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Hi Bold Bakers!

WHY YOU’LL LOVE THIS RECIPE: This simple yet Chef-Gemma-approved Jumbo Lemon Blueberry Costco Muffins recipe saves you a trip to a crowded Costco! These giant muffins are moist and tender, loaded with beautiful floral flavor from vanilla and sweet blueberries, and elevated with refreshing lemon zest. One bite is enough to convince you that homemade Lemon Blueberry Costco Muffins can be even better and might be your new favorite! 

In less than an hour, you’ll have your kitchen smelling wonderful with these irresistible homemade Lemon Blueberry Muffins. Also don’t miss my Crazy Muffins recipe: A one-stop shop for muffin basics and endless flavor variations!

Table Of Contents

What Are Jumbo Lemon Blueberry Costco Muffins?

Lemon Blueberry Muffins are a muffin variation consisting of fresh lemon zest and blueberries. These muffins are characteristic of their sweet and tart flavor combination alongside their moist and fluffy texture. The biggest difference in this recipe is that, just like Costco muffins, they’re jumbo – and who doesn’t love jumbo muffins?

Homemade giant Costco muffins on the cooling rack, with crispy golden brown crust and bursting with floral juicy blueberries.

These muffins are one of the most popular flavors and are great to eat for brunch, dessert, or as a snack. Because they contain tangy ingredients such as buttermilk and plain yogurt and they’re jumbo-sized, it makes them extra moist and more hearty than ordinary muffins.

Love these Homemade Lemon Blueberry Muffins? Then you should try my other lemon blueberry desserts: Gluten-Free Pound Cake, Crepes, Popsicles, Cheesecake Bars, Eton Mess, and Curd Bread Pudding!

Ingredients You Need for Lemon Blueberry Costco Muffins and Why:

Dry Ingredients

  • All-purpose flour: All-purpose flour has 9-11% protein content which will help bind all of your wet and dry ingredients together and create the base of your muffins.
  • Granulated sugar:
    • Granulated sugar is also known as white sugar.
    • Granulated sugar not only perfectly sweetens your muffins, but also coats air bubbles in the batter to stabilize the aerated structure for a light and fluffy result.
  • Baking powder:
    • Most Baking powder on the market is “double-acting”. Besides activating through heat during baking, baking powder gets ACTIVATED IMMEDIATELY mixed with wet ingredients. DO NOT let the batter sit for too long. Bake it off ASAP for the best rise without losing effectiveness.
    • Baking powder contains dry acid “cream of tartar” so can get activated with any liquid that doesn’t have to be acidic to leaven baked goods.
  • Salt: A pinch of salt will add depth and structure to your muffins while balancing the sweetness.
  • Baking soda:
    • Baking soda doesn’t contain acid, so it activates ONLY when mixed with acidic ingredients like buttermilk and yogurt.
    • Baking soda reacts with acid from buttermilk and yogurt also eggs to release gas, which creates air pockets to make muffins rise.
    • Baking soda also reacts with hot sugar to give the muffins a crispy skin.

Wet Ingredients

  • Eggs:
    • Eggs always need to be at room temperature in baking unless specified otherwise.
    • Eggs enrich flavors, provide emulsifier from yolks to bind all ingredient homogeneously, and incorporate and retain with egg whites to make muffins fluffy and soft.
  • Buttermilk:
    • Buttermilk is a tangy, acidic dairy product made by adding bacteria culture to milk.
    • Buttermilk adds a perfectly tangy flavor, implements tons of moisture and tenderizes muffins. 
  • Vegetable oil:
    • Oil is all fat without water so it doesn’t contribute to gluten strands.
    • Oil provides fat to retain air which keeps muffins extra moist and light, and most importantly helps prevent your muffins from going stale.
  • Plain yogurt:
    • In order not to interfere with the lemon or blubbery flavor, use plain yogurt.
    • You can make plain yogurt using my How to Make Yogurt recipe! 
    • Yogurt contains acid to tenderize the gluten to make muffins extremely soft.
  • Butter:
    • Melted butter is crucial for buttery, rich flavors and moist textures in muffins.
    • Butter also contribute to the nice golden brown crust of your muffins.
    • To melt your butter, place pieces of it in a microwave-safe bowl and microwave for about 30 to 45 seconds. If there are any leftover pieces, stir them around and they should melt away.


  • Lemon zest: You can’t have Lemon Blueberry Muffins without lemon zest! The lemon peel holds the most lemon flavor and will add a fresh citrusy flavor.
  • Vanilla extract: Vanilla extract elevates flavor and sweetness in muffins. Try making Homemade Vanilla Extract from scratch!
  • Blueberries:
    • Blueberries not only pack great sweet and tart flavors, but also add an indigo pop of color to your muffins.
    • Feel free to use fresh or frozen blueberries. DO NOT thaw frozen blueberries. 

Homemade Lemon Blueberry Costco Muffins Recipe Ingredients

How To Make Lemon Blueberry Costco Muffins:

  • Before baking:
    • Preheat the oven and generously butter a muffin tin. You can also use a standard-sized cupcake pan and bake for a shorter time.
    • Making the batter:
      • DO NOT over mix. Prepare dry and wet ingredients separately then combine them JUST until everything comes together.
      • Gently fold in fresh or FROZEN blueberries. DO NOT thaw frozen blueberries to avoid wetting the batter.
    • Divide the batter evenly among the muffin cups.

Step-by-step instructions on how to make Lemon Blueberry muffins. Mix dry and wet ingredients in two separate bowls then mix until JUST combined. Gently fold in blueberries.

  • Baking:
    • Bake on a middle rack in the oven until golden on top and a skewer inserted into the center comes out clean.
  • After baking:
    • Let cool in the pan before removing. Serve warm or at room temperature.

Scooping the batter into prepared greased muffin tin before baking. Cooling in the tin after baking.

Gluten-Free, Vegan Lemon Blueberry Costco Muffins

Note: Making substitutions may change the texture and flavor of your muffins. Use whatever you have on hand or whatever works best for you. When in doubt, experiment!

Can I Make Lemon Blueberry Costco Muffins Ahead Of Time?

  • You can NOT make the muffins batter ahead of time and let it sit without affecting their oven spring. Because baking powder gets activated the moment mixed with any type of wet ingredients. 
  • However, you can mix all ingredients BESIDE baking powder and baking soda ahead of time.
    • Keep the mixture in the fridge for up to 3 days.
    • When ready to bake, sprinkle baking powder and baking soda over the batter then gently fold them in. In this case, take care not to over mix! Then proceed per this recipe.
    • The obvious benefit of making the muffin batter in advance is to manage baking time with less stress. The bonus is that muffins tend to be a little softer from extra time for dry ingredient to get hydrated to lock in moisture.

How To Store Lemon Blueberry Costco Muffins

  • Room temperature: The best way to store leftover Lemon Blueberry Muffins is to keep them in an airtight container (after cooling completely) at room temperature for up to 2 days. 
  • Refrigerator & Freezer: You can also store muffins in an airtight container in the fridge for up to 5 days or in the freezer for up to 3 months.
  • To reheat frozen muffins, let them thaw at room temperature then wrap them with aluminum foil and bake in the oven at 350°F/180°C for 10-25 minutes. Or pop them directly into the microwave for about 20 to 30 seconds.


Should I use frozen or fresh blueberries for muffins?

  • Fresh blueberries: It’s nearing blueberry season, so it’s the perfect time to get some practice in with some fresh blueberries. Fresh blueberries may be on the tart side, so if you want to sweeten your muffins, I suggest adding a bit more sugar.
  • Frozen blueberries:
    • I recommend using frozen blueberries because they are frozen during peak season, making them extra sweet and ripe.
    • Be sure to use them straight from frozen so that it doesn’t add extra moisture to your muffin batter.

Can I substitute regular milk for buttermilk in this recipe? What can be used in place of buttermilk?

  • No, do not substitute a neutral liquid milk for an acidic buttermilk. Milk lacks enough acid to react with the raising agent to make muffins rise well.
  • The acid will react with a raising agent to release gas to yield a good rise and  will break down protein in flour to make baked goods softer. In this way, the protein won’t have big holes so moisture will be lockedd in. So you will get soft and moist results.
  • Buttermilk, plain yogurt, and sour cream can substitute one for another and you make them at home!
    • Buttermilk is thinner so you want to use up to 3/4 in one go and adjust it to get the same consistency as the recipe.
    • Strained or Greek yogurt works the best among yogurt.

Can I use lemon juice instead of lemon zest?

Yes, you can substitute them with lemon juice if you don’t have fresh lemons for lemon zest. However, the lemon flavor will be less present.

  • This is because the peel of lemons carries the strong lemon flavor that we all know. Additionally, lemon juice tends to be more acidic than lemon zest, so experiment with small amounts to balance the flavors.
  • To substitute, you can incorporate about 6 tablespoons of lemon juice for every tablespoon of lemon zest. Be sure to note that the more liquid you add to your muffins, the less fluffy your muffins may turn out.

Can I use muffin liners?

  • Yes, you can totally use muffin liners if you want an easier time taking out the muffins or make them easy to grab and go.
  • The main difference with using liners instead of greasing your muffin tin is that your muffins may not be as crispy on the outside and they can get stuck to your liners.

Why are my muffins soggy? How do I prevent soggy muffins?

Your muffins can turn out soggy if you leave them to cool in the muffin pan for too long or if there was too much moisture on and in your ingredients. To prevent soggy muffins try the following tips:

  • Remove muffins from tin: Leaving your muffins to cool too long in the muffin tin causes steam to trap between the muffin bottom and the tin. Make sure to take your muffins out at the 15-minute mark to ensure your muffins won’t be soggy.
  • Remove excess moisture: The primary culprit to an overall soggy muffin is too much moisture. Be sure to pat your blueberries and lemon dry if fresh from washing. If using blueberries from frozen, don’t thaw them before use. Condensation will develop on the outside of the blueberries and internally make them too juicy. 

How do I get my muffins out of the tin? How to prevent muffins from breaking?

To get your muffins out of the tin without breaking them, let them cool for 15 minutes. Gently run a butter knife along the sides of the tin to loosen your muffins. Waiting to remove your muffins will allow your muffins to firm up and release them from the sides of the tin.

Gemma’s Pro Chef Tips:

  • To make the Costco-size muffins, you need a Jumbo Muffin Tin. However, you can use this batter to make 12 regular muffins. Bake at 350°F (180°C) and for 15-20 minutes. 
  • Be sure to use room-temperature ingredients for the best results.
  • If using frozen blueberries, don’t thaw them or they will release too much juice into the batter.
  • To evenly divide your batter, use an ice cream scoop!
  • For easy removal, gently slide a butter knife around the edges of your muffin tin to loosen your muffins. They should easily pop out.
  • Feel free to replace the blueberries with blackberries or raspberries. I don’t recommend strawberries as they release too much water when baking and throw off the texture of the muffins.
  • Add some chocolate chips for added sweetness and chocolate flavor!

Half of a muffin in front loaded with juicy blueberries, showing the soft and bubbly tender inside. Other muffins are in the back.

And don’t miss more everyday baking recipes in my NEW Bigger Bolder Baking Every Day Cookbook!

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