Giant Costco Copycat Gluten Free Strawberry Rhubarb Muffins

Strawberry rhubarb is one of those classic combos that reminds me of summer potlucks, with bowls of pasta salad and cornbread and hot dogs and hamburgers and flimsy paper plates and plastic cups. Hot, southern Oregon summers (for those of you not from the Pacific Northwest, southern Oregon is not the same as Portland/Seattle – those two cities perpetually washed in grey and rain – it’s actually darn hot, sunny, and dry from May-September). So here I am, wishing for a hot southern Oregon summer, making these MASSIVE gluten free strawberry rhubarb muffins because that’s as close as we’re gonna get for now.

And for those of you new to this strange phenomenon: we started a series of GIANT gluten free Costco copycat muffins a while back, out of a nostalgic longing for those big-as-your-face muffins we used to get as kids from Costco for road trip treats, Girl Scout Troop meeting snacks, and all other special occasions. And for those of you prone to knocking negatively on bulk baked goods or Costco bakery items because they’re cheap, high in carbs (duh, stay away from the baked goods hun), and not high-quality, take a seat and examine your socio-economic privilege while you snack on the phrase “live and let live.” For those of you who fondly remember these like we do, read on and make yourself one (or two) batches and have a ball. And then make all these other giant muffins because why the heck not: giant poppyseed muffins, giant blueberry muffins, giant chocolate chip muffins, giant double chocolate muffins, giant banana nut muffins.

Tips for Fantastic Giant Muffins

A few tips for getting these to turn out just like you remember those Costco muffins:

• Use the right-size of pan! Apparently, Costco keeps their giant muffin pans as a trade secret because we can’t find them ANYWHERE on the internet and you can find EVERYTHING on the internet. Bravo, Costco, for a secret well-kept. However, we’ve found a way to crack the code and gone ahead and just used these brilliant 4-inch cake pans because, after careful inspection, we’ve discovered that Costco muffins are exactly 4-inches in diameter! HA! Take that, Costco-bakery-lords. I never thought I’d be regularly using 4-inch cake pans but here we are. I’ll just need to make a bunch of tiny cake recipes next!
• Let your batter REST, per the recipe, for at least 30 minutes. For two reasons: 1) the batter thickens as it rests which is incredibly important for a muffin filled with heavy chunks of fruit! A thicker batter will help suspend all of the strawberry + rhubarb pieces all throughout your muffins, ensuring every bite has the perfect ratio of fluffy muffin to fruit; and 2) something somewhere said that baking powder needs a bit more time to “activate.” Don’t quote me on this, who knows if it’s actually true.
• Don’t over-mix your batter! Muffins need a lot of lift, especially these giant ones, and if you over-mix your batter, you’ll end up with flat or sunken muffins which is no fun.
• Use a good 1-1 gluten free flour mix! We use the Bob’s Red Mill one (the baking mix), though we’ve heard good things about Cup-4-Cup. We’ve only tested this recipe with this one so if you want them to turn out exactly like ours, we recommend snagging a bag of that specific 1-1 gluten free flour.
• Do NOT open the oven door during baking time. Tape it shut if you have to! You can certainly turn on the oven light and peek and the gloriousness that is a set of rising muffins nearly-ready to be devoured, but do not open that door! Opening the door will immediately lower the oven temp and prohibit your muffins from rising correctly. If you’re in the last few minutes of baking and need to test to see if they’re done, open the oven just a tiny bit and reach in and just tap the top of one – if it springs back it’s done, if it presses in like a foam mattress topper, it’s not and needs a couple more minutes!
• These will keep in an airtight container (or in ziplock baggies) for a week or so – and they freeze REALLY well! So if you want to make a batch and save a bunch, put them in a sturdy plastic container or a freezer plastic bag and pop them in there. Then microwave for about 30-45 seconds (from frozen) before eating! I even like popping mine in the microwave for 10-15 seconds from room temp to get them all warm and floofy again before eating.

Print Recipe

4 from 2 votes

Giant Costco Copycat Gluten Free Strawberry Rhubarb Muffins

These are the perfect spring breakfast treat – or snack! – packed with fresh rhubarb and strawberries

Prep Time20 minutes mins

Cook Time40 minutes mins

Cooling time15 minutes mins

Course: Breakfast, Snack

Cuisine: American

Diet: Gluten Free

Keyword: breakfast, costco muffins, easy, giant, gluten free, muffins, rhubarb, strawberry, strawberry rhubarb

Servings: 6 giant muffins

Calories: 500kcal

Author: Amelia Farber

Equipment

• Six 4-inch round cake pans – link below
• Small saucepan

Ingredients

• 4 large eggs
• 1 1/2 Cups white sugar
• 1/2 Cup canola oil
• 2/3 Cup salted butter browned (instructions below)
• 1 Cup milk
• 1/2 Cup sour cream
• 2 1/2 tsp vanilla extract
• 1/4 tsp ground ginger
• 2 Cups gluten fre 1-1 flour mix with xanthan gum included (if your mix does not have xanthan gum, add 1 teaspoon of it now)
• 1/2 Cup sweet rice flour
• 1/2 Cup packed blanched almond flour
• 2 3/4 tsp baking powder
• 3/4 tsp salt
• 1 1/2 Cups hulled chopped strawberries – plus a few extra for topping into 1/2 inch pieces
• 1 1/2 Cups peels and chopped rhubarb – plus a few extra for topping into 1/2 inch slices

Instructions

• First, make your browned butter! In a small saucepan over medium-low heat, melt the 3/4 cup of salted butter and stir constantly until melted and simmering. Continue to simmer, on medium heat, for at least a few minutes, until the popping and hissing sounds have completely subsided (this is the water in the butter burning off – you’ll know once it’s silent). Continue to cook, stirring constantly, until the butter reaches a deep amber color and smells nutty or caramelly. The butter may foam, so keep stirring/lifting up spoonfuls of the butter to see the color. The browned milk solids will foam up in the center of the pan – once it does that- immediately take off the burner and let sit for a few minutes, then pour (scrape ALL of the brown bits – that's the flavor!) into a heat-proof small bowl and let it cool to just above room temp (but not solid).
• Once your browned butter is cooled but still liquid, make your muffin batter! It will need to rest for 30 minutes before baking. In a large bowl, whisk together the eggs, sugar, oil, melted cooled browned butter (you'll end up with about 1/2 cup of browned butter), sour cream, milk, and vanilla and ginger. Then, in a medium bowl, whisk together the gluten free 1-1 flour mix, sweet rice flour, almond flour, baking powder, and salt, then dump dry ingredients into the wet bowl and whisk until fully combined. Finally, fold in 1 1/2 cups each of the strawberries and rhubarb (save the rest for sprinkling on top of each muffin). Let the batter sit at room temp for 30 minutes.
• Finally, preheat the oven to 425° Fahrenheit and place your six 4-inch cake pans on a cookie sheet. Spray each pan with cooking spray, then spoon batter into each one evenly (they should be about 2/3-3/4 full) and sprinkle the leftover chopped strawberries and rhubarb on top of each one (just a few pieces on top of each). Bake for 5 minutes at 425 then immediately lower the temp to 350° F (do NOT open the oven door!) and let bake for 25-30 more minutes until the tops spring back with touched. Let cool nearly-completely before turning out and eating!

Tag @sisterssansgluten on Instagram if you snap a photo of your muffins!

Food photography and styling by Amelia Farber