Blueberry Crumble Bars with Oats
Get all the flavor of blueberry crisp in a dessert bar. These blueberry crumble bars have a buttery oat crumble and juicy berry filling. They are easy to make from scratch too!
I get so excited when summer comes around because it means baking with berries! They provide the best natural flavor in desserts. To kick off the summer baking, I’m introducing a new variation of my crumble bars using blueberries. You’ll want to bake this recipe all summer long.
Why You’ll Love This Recipe
- Satisfying contrasting texture. Buttery crust topped with blueberries bursting with fresh flavor and topped with a crisp crumble—how delicious does that sound?
- Reliable recipe. I use this oatmeal crust and crumb topping for various recipes, like my strawberry oatmeal bars, and then swap out the fruit filling!
- Great use of seasonal blueberries. Stop by your local farmers market and get the berries while they are in season. It will make the bars all the more flavorful.
- Perfect for summer gatherings. Be it backyard barbecues, pool parties or Fourth of July festivities, these blueberry bars are guaranteed to be a popular treat.
Ingredient Notes
- Blueberries: Fresh blueberries are preferred, but frozen can also be used.
- Oats: Rolled oats add a chewy texture to the crumble. I do not recommend steel-cut oat since they are too gritty, but quick oats can be used in a pinch.
- Butter: Unsalted butter binds the ingredients for the crust in crumble. Make sure it’s softened, but still cool.
- Brown sugar: To help with the chewy crumble texture, brown sugar used (light or dark is okay).
- Sugar: The filling is sweetened with granulated sugar.
- Cornstarch: To thicken the fruit filling, a tablespoon of cornstarch is stirred into the mixture.
- Lemon juice: Fresh squeezed lemon juice helps highlight the blueberry flavor.
Refer to the recipe card for full list of ingredients and measurements.
Recipe Variations
Add a drizzle of icing. Whisk together 1/2 cup confectioners’ sugar and 1 Tablespoon fresh lemon juice. Drizzle over the bars after they have cooled.
Mix up the berries. Add some raspberries and blackberries to the mix! Total amount of berries used should equal two cups. You can also use 3/4 preserves instead of fresh berries, like I do for my raspberry oatmeal bars.
Double the recipe. Double all the ingredients and bake in a metal 9×13 baking pan (yields 24 bars). Baking time will be the same.
How to Make Blueberry Crumble Bars
- Make the crumble and oat mixture. Whisk together the flour, oats, brown sugar, sugar, baking powder and salt. Add the butter and vanilla, then mix to combine.
- Bake the crust. Transfer half the oat mixture to an 8×8 baking pan. Press down firmly. Bake at 350 F for 20 minutes.
- Cook the blueberry filling. In a saucepan over medium heat, cook the blueberries, sugar, cornstarch and lemon juice. Stir frequently until thickened. Remove from heat.
- Transfer blueberry mixture to baked crust. Sprinkle remaining oat mixture on top. Bake for 30 more minutes at 350 F. Cool completely before slicing and serving.
Expert Tips
Use fresh blueberries. They have more flavor and taste better! Frozen berries can work, but they get watery when cooked so the filling will have a different texture.
Cool the bars completely before cutting. In order for the layers to set, the bars need time to cool. If they are still warm when cut, they will be very messy.
Make Ahead and Storage Tips
Make ahead the crumble mixture and store covered in the refrigerator for up to 48 hours. The blueberry filling can also be made ahead of time and stored in the refrigerator. Bring both to room temperature before assembling and baking.
Store bars in an airtight container at room temperature for up to 3 days or in the refrigerator for 5 days.
Freeze for up to 3 months. Once the bars have cooled, wrap in plastic wrap and store in a freezer bag or airtight container to prevent freezer burn. Defrost in the refrigerator before bringing to room temperature and serving.
Recipe FAQ
Yes, but let them defrost first and discard any juices. If the filling is too liquid-y, add and extra Tablespoon of cornstarch or flour.
Yes, but the texture will be slightly different. The crumble will be a little less chewy and crisp.
They are supposed to be crumbly, but if they are not holding their shape then it’s possible they were underbaked. It’s also important to let the bars completely cool so they are set before cutting.
I haven’t tested this, but I have made these bars with fruit preserves and jam. Use about 3/4 cup blueberry jam if trying this method.
Related Recipes
If you enjoyed this recipe, try these desserts next!
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Get the Recipe: Blueberry Crumble Bars with Oats
Ingredients
Crust and Topping
- 1 ½ cups (187 g) all purpose flour
- 1 ½ cups (150 g) rolled oats
- ⅓ cup (66 g) packed light brown sugar
- ⅓ cup (66 g) granulated sugar
- ¼ teaspoon baking powder
- ¼ teaspoon salt
- ¾ cup (12 Tablespoons or 170 g) unsalted butter, softened, but still cool, cut into 1/2-inch pieces
- 1 teaspoon pure vanilla extract
Blueberry Filling
- 2 cups (538 g) fresh blueberries
- ¼ cup (50 g) granulated sugar
- 1 Tablespoon (9 g) cornstarch
- 1 ½ Tablespoon (22 ml) lemon juice
Instructions
- Preheat oven to 350℉. Line a 8×8 baking dish with parchment paper and set aside.
- In the bowl of a stand mixer (or using a hand mixer), combine flour, oats, brown sugar, granulated sugar, baking powder and salt. Mix for 30 seconds until thoroughly combined. With the mixer on low, add the butter and vanilla extract. Mix until the mixture resembles coarse sand (about 2 minutes).
- Transfer half the mixture to prepared pan. Use your hands or the back of a measuring cup to press mixture evenly into the bottom to form the crust. Bake crust for 20 minutes or until golden (keep the oven on).
- While the crust bakes, make the blueberry filling. Bring blueberries, sugar, cornstarch, and lemon juice to a boil in a saucepan, stirring constantly, until mixture is thickened, about 2 minutes. Remove from heat. Cool slightly.
- Spread berry mixture over baked crust. Sprinkle remaining oat mixture evenly over the fruit layer.
- Bake bars for 30 to 35 minutes or until the blueberries bubble and the top is golden brown. Allow bars to cool completely before removing from pan and cutting into 16 squares.
