These blueberry oatmeal crumble bars are filled with juicy blueberries and a crunchy oatmeal crumble. They work with fresh or frozen berries, and the same oatmeal mixture is used for both the base and the topping. Serve as a dessert with ice cream or enjoy leftovers for a special breakfast.
This recipe was updated August 16, 2020 with new photos, tips, and storage instructions
My blueberry crisp bars are a favorite in spring and summer — a buttery shortbread base layered with fresh blueberries and a crunchy crumble. I wanted a version with an oatmeal crumble because oats make everything feel breakfast-friendly, and they add a lovely crunchy texture that stands up to juicy fruit.
The result is blueberry oatmeal crumble bars: a crunchy oatmeal cookie base, a thick layer of juicy blueberries, and a cinnamon-oat crumble on top. The oats give great texture and hold up well under the berries.
These bars are great for breakfast (not much worse than sugary cereal) or topped with vanilla ice cream for dessert. I also enjoy them straight from the fridge — they’re delicious cold.
Blueberry Oatmeal Crumble Bar Recipe
A convenient feature of this recipe is that the same oatmeal mixture makes both the base and the crumble topping. Start by whisking flour, old-fashioned oats, granulated sugar, a bit of cinnamon, and salt. Stir in melted butter and one egg yolk. Make sure to use old-fashioned or large-flake oats — quick or instant oats lack the texture needed here.
Reserve about 3/4 to 1 cup of the oat mixture for the crumble topping, and press the remaining mixture into the bottom of the pan to form the oatmeal base.
The blueberry filling is simple: blueberries, fresh lemon juice, a little sugar, and cornstarch. You can use fresh or frozen berries; frozen will need slightly longer baking time. Lemon juice brightens the flavor and helps soften the berries, while cornstarch thickens the filling.
Spoon the blueberry mixture over the pressed oatmeal base, covering it completely. Crumble the reserved oatmeal mixture (mixed with a tablespoon of brown sugar) over the berries to form a crunchy topping. Then bake until the berries are bubbling and the crumble is golden.
These bars deliver a great mix of texture and bright berry flavor. I like to make them for dessert and keep leftovers for breakfast the next day.
Recipe Video
For other fruit crumble bars, try peach, raspberry, or apple variations. For more blueberry ideas, consider blueberry bread, a classic crumble, or blueberry coffee cake.
Blueberry Oatmeal Crumble Bars
Equipment
- 8×8 inch (20×20 cm) baking pan
Ingredients
For the Base & Crumble Topping
- 1 cup all-purpose flour
- 3/4 cup old-fashioned oats (large flake oats, not quick or instant)
- 1/2 cup granulated sugar
- 1/4 cup packed brown sugar
- 1/2 teaspoon cinnamon
- 1/4 teaspoon salt
- 1/2 cup unsalted butter, melted
- 1 large egg yolk (discard the white)
- 1 tablespoon packed brown sugar (for the topping)
For the Blueberry Layer
- 2 cups blueberries (fresh or frozen; increase bake time for frozen)
- 1 tablespoon lemon juice, freshly squeezed
- 1/4 cup granulated sugar
- 2 teaspoons cornstarch
Instructions
- Preheat the oven to 350°F (175°C). Line an 8×8 inch pan with parchment paper, leaving an overhang, or use foil and grease it well.
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Oatmeal Base & Topping
- In a medium bowl whisk together the flour, oats, granulated sugar, 1/4 cup brown sugar, cinnamon, and salt.
- Stir in the melted butter and egg yolk until combined. If the mixture feels very buttery, add 1 extra tablespoon of flour.
- Remove about 1 cup of the mixture and mix it with the additional tablespoon of brown sugar for the topping.
- Press the remaining mixture firmly into the bottom of the prepared pan to form the base.
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Blueberry Layer
- In a medium bowl toss the blueberries with lemon juice, 1/4 cup sugar, and cornstarch until evenly coated.
- Spoon the blueberry mixture evenly over the oatmeal base.
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Assembly and Baking
- Crumble the reserved oatmeal mixture over the blueberry layer, forming clumps with your fingers or by squeezing in your fist.
- Bake for 45–55 minutes, until the berries are bubbling and the top is golden. If using frozen berries, bake 50–60 minutes.
- Cool completely in the pan until room temperature, at least 3 hours, before slicing.
- Use the parchment or foil overhang to lift the slab from the pan and slice with a sharp knife.
- Serve chilled, at room temperature, or warmed. Optionally add a scoop of ice cream.
Notes
- Use old-fashioned rolled oats. Do not substitute quick, instant, or steel-cut oats.
- If the oatmeal mixture seems too wet, add 1–2 tablespoons more flour as needed.
- This recipe is for an 8×8 inch (20×20 cm) pan. It will not fully fill a 9×9 inch pan.
- To double the recipe, double all ingredients and bake in a 9×13 inch pan; bake time remains similar.
- Nutrition is an estimate per bar, based on 9 slices.
- Store bars in an airtight container in the refrigerator for up to 4 days. Freeze for up to 2 months and thaw in the fridge.