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These blueberry oatmeal bars are soft, buttery, and packed with juicy berries! Sweet, tangy, and perfect for an easy dessert or afternoon treat.
Know Before You Scroll
Flavor Profile
Buttery, soft, and crumbly with warm cinnamon notes and bursts of juicy blueberries. Bright lemon cuts through the sweetness for the perfect fruity balance.
Difficulty Level
Easy. Just mix, layer, and bake. No special techniques or stress—just wholesome, cozy baking.
Equipment Needed
9-inch square baking pan, parchment paper, two mixing bowls, measuring cups, whisk, spoon, spatula, oven.
Top Tip
Let the bars cool completely before slicing! They’ll hold together better and give you those clean bakery-style edges.
Time-Saving Tips
Use frozen blueberries to skip washing and sorting. Just make sure to thaw and drain them well first!
Ingredient Swaps
No fresh lemon? A splash of bottled lemon juice will do in a pinch. Gluten-free flour works great here too if you need it!
What You’ll Need
All-purpose flour, old-fashioned rolled oats, packed light brown sugar, granulated sugar, baking powder, ground cinnamon, salt, unsalted butter, fresh or frozen blueberries, cornstarch, lemon juice, lemon zest.
Cozy Crumble of Summer Sweetness
I’ve been chasing the perfect blueberry oatmeal bars for what feels like forever. The kind that’s soft and buttery on the bottom, jammy and juicy in the middle, and finished with a golden oat crumble that actually sticks. I tested versions with coconut oil—too greasy. Tried less butter—too dry. One batch went full-on granola bar, and it was a nope. What finally worked? This balance right here. A soft oat crust, a thick pile of fresh blueberries, and just enough lemon to make it pop. Whether they’re served as is or topped with vanilla ice cream, these blueberry oatmeal bars are simple, nostalgic, and honestly everything I wanted in one bite.
Ingredient Notes
Blueberries
Best Choice
Fresh blueberries are ideal for the best texture and color. Sweet, ripe berries hold up beautifully during baking.
Substitutions
Frozen blueberries totally work—just thaw and strain them to avoid a soggy crust.
Sugar
Best Choice
A mix of light brown sugar and white granulated sugar gives you that golden, slightly caramelized flavor in the crust while keeping the filling bright and sweet.
Substitutions
You can use all brown sugar for a richer, slightly softer crust, or all granulated sugar for a lighter, more crumbly texture. Both work just fine—it really comes down to what you have on hand.
Spice
Best Choice
Just a hint of cinnamon warms up the oat mixture without overpowering the blueberries.
Substitutions
Pumpkin pie spice or apple pie spice can be used if you’re feeling creative.
Lemon
Best Choice
Fresh lemon is the way to go here—both the juice and the zest bring a bright, citrusy pop that makes the blueberry flavor sing. Zest the lemon before juicing to get the most out of it.
Substitutions
If you’re out of lemons, store bought orange juice can work in a pinch. It’ll be slightly sweeter and less tart, but still adds that fresh citrus note.
Flour
Best Choice
Stick with regular unbleached all-purpose flour—it gives the crust structure without making it dense.
Substitutions
A 1:1 gluten-free flour blend works great if you need a gluten-free version.
Oats
Best Choice
Old-fashioned oats are key for that hearty, chewy texture. They bake up soft but still hold their shape.
Substitutions
Quick oats can work in a pinch but will make the bars softer and less structured.
Butter
Best Choice
Unsalted butter gives you control over the salt level—plus, it melts beautifully into the oats.
Substitutions
Salted butter is totally fine—just skip the added salt in the recipe.
Where to Find:
Cereal aisle or bulk section, sometimes near the granola.
Cornstarch
Best Choice
Cornstarch (Also known as cornflour in some countries), thickens the blueberry filling so it doesn’t run when sliced.
Substitutions
Arrowroot powder or tapioca starch also work well.
Where to Find:
Usually in the baking aisle near flour and cocoa powder.
You can find the full, printable recipe at the top of this post, but you can read the detailed instructions with photos for each step below.
Step By Step Instructions
1
Prepare the Crust and Topping Mixture
In a bowl, I’m whisking together 1 and ½ cups of all-purpose flour, 1 cup of old-fashioned oats, ¼ cup of packed light brown sugar, ¼ cup of granulated sugar, 1 teaspoon baking powder, ½ teaspoon cinnamon, and ¼ teaspoon salt. Just give that a quick mix. pour in 10 tablespoons of melted butter. Yes, ten. Stir it all together until you get that perfect crumbly texture—moist, but not wet.
2
Make The Base
Scoop out 2 cups of that mixture and press it firmly into a parchment-lined 9-inch square pan. Use your hands or a measuring cup to get it nice and even.
Pop that in the oven at 350°F/177°C for 10 minutes. Let it set up just a bit while we move on.
3
Mix The Filling
In a separate bowl, I’m mixing 4 and ½ cups of fresh blueberries—frozen totally works too, just thaw and drain them first. Add ⅓ cup of sugar, 2 tablespoons of cornstarch, 1 tablespoon of lemon juice, and a little lemon zest—about a teaspoon.
Gently stir it all up until those berries are coated in that light, sugary glaze. It’s gonna bubble up so nicely in the oven.
4
Assemble
Pour that juicy blueberry mix right over the crust—spread it out so it’s evenly layered.
Then crumble the rest of the oat mixture on top. Not too perfect—just scattered like a good streusel.
5
Bake
Bake it at 350 for 35 to 40 minutes, until the top is golden and the blueberries are thick and jammy and bubbling around the edges. Cover with foil if it’s getting too brown too fast.
6
Cool and Slice
Once it’s baked, be patient—let the bars cool completely in the pan. This part is key.
When they’re cool, lift them out using the parchment, slice into squares, and enjoy that soft, crumbly, lemony, berry-filled goodness.
More Blueberry Goodness
Recipe
Blueberry Oatmeal Bars
Ingredients
For the Crust & Topping:
- 1½ cup all-purpose flour
- 1 cup old-fashioned rolled oats (divided)
- ¼ cup light brown sugar (packed)
- ¼ cup granulated sugar
- 1 teaspoon baking powder
- ½ teaspoon ground cinnamon
- ¼ teaspoon salt
- 10 Tablespoons unsalted butter (melted)
For the Blueberry Filling:
- 4½ cups fresh blueberries (if frozen, thaw and strain the liquid)
- ⅓ cup granulated sugar (reduced from ½ cup)
- 2 tablespoons cornstarch
- 1 tablespoon lemon juice
- 1 teaspoon lemon zest
Instructions
- Preheat your oven to 350°F (177°C). Prepare a 9-inch square baking pan (this one and this one are my favorites) by lining it with parchment paper, leaving some overhang on the sides for easy removal of the bars. Set it aside.
Prepare the Crust & Topping
- In a medium bowl, whisk together the flour, 1 cup of oats, brown sugar, granulated sugar, baking powder,, cinnamon, and salt.
- Pour in the melted butter and mix until moist and crumbly with no dry patches. Take 2 cups of the mixture and press it firmly into the prepared baking pan using your hands or the bottom of a measuring cup to create an even crust. Bake for 10 minutes, then remove from the oven and let it cool slightly.
- Then sprinkle the remaining oats over the surface of the base and set aside.
Prepare the Blueberry Filling
- In another bowl, combine blueberries, granulated sugar, cornstarch, lemon juice, and lemon zest.. Stir gently until the berries are well coated.
Assemble & Bake
- Spread the blueberry mixture evenly over the crust. Sprinkle the reserved crust mixture over the blueberries.
- Bake for 35–40 minutes, or until the topping is lightly golden and the blueberries are thick and bubbling. You can cover the pan with foil if the topping begins to brown too quickly.
Cool & Serve
- Let the bars cool completely in the pan before lifting them out using the parchment overhang. Once cooled, slice into squares and serve.
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FAQs
Can I use frozen blueberries instead of fresh?
Yes. Just make sure they’re thawed and well-drained. Excess liquid can make the bars a little soggy. If your berries are still frozen, you can use them—just know they might bleed a bit more color into the filling.
Can I make these gluten-free?
Yes! Just swap the all-purpose flour for a good 1:1 gluten-free baking blend. And double-check your oats to make sure they’re certified gluten-free.
Do I need to refrigerate the leftovers?
Not necessarily. They’re fine at room temp for a couple of days, especially if your kitchen isn’t super warm. But if you want them to last longer or keep their structure, the fridge is your best friend.
Can I freeze the bars whole?
Absolutely. Cool the whole pan, wrap it tightly with plastic wrap and foil, and freeze the full slab. When you’re ready, thaw in the fridge, then slice and serve. It’s great for make-ahead brunches or gifting.
Why do I need to let them cool before slicing?
Because if you cut them too soon, they’ll fall apart! The filling needs time to set, and the crust firms up as it cools. Give them a good hour or two at room temp for the cleanest, prettiest slices.
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