Can I use frozen blueberries for crumble bars?

Yes, you can use either fresh or frozen blueberries. If using frozen, do not thaw them first, but keep in mind you will likely need to add an extra 5 to 10 minutes to the total baking time.

What kind of oats are best for oatmeal crumble bars?

It is highly recommended to use old-fashioned rolled oats (or large flake oats) for the best crunchy texture. Quick oats and instant oats behave too much like flour and will make your crumble mushy.

How long do blueberry crumble bars last?

Once completely cooled, you can store these blueberry bars in an airtight container in the refrigerator for up to 4 days. You can also freeze them for up to 2 months.

Do I need to make a separate dough for the crust and the topping?

No! One of the best parts about this easy recipe is that the oatmeal mixture doubles as both the sturdy cookie base and the crunchy crumble topping.

The Best Blueberry Oatmeal Crumble Bars 2026

Blueberry Oatmeal Crumble Bars

Print Recipe

Author: Maya
Prep Time: 15 minutes
Cook Time: 50 minutes
Total Time: 65 minutes
Yield: 9 slices

Ingredients

For the Base & Crumble Topping:

1 cup all-purpose flour
¾ cup old-fashioned rolled oats (do not use quick oats)
½ cup granulated sugar
¼ cup packed light brown sugar
½ teaspoon ground cinnamon
¼ teaspoon salt
½ cup unsalted butter, melted
1 large egg yolk (discard the white)
1 tablespoon packed brown sugar (reserved for topping)

For the Blueberry Layer:

2 cups blueberries (fresh or frozen)
1 tablespoon fresh lemon juice
¼ cup granulated sugar
2 teaspoons cornstarch

Instructions

Preheat & Prep: Preheat oven to 350°F (175°C). Line an 8×8 inch baking pan with parchment paper, leaving an overhang on the sides for easy removal.
Mix Dry Ingredients: In a medium bowl, whisk together the flour, oats, granulated sugar, ¼ cup brown sugar, cinnamon, and salt.
Add Wet Ingredients: Pour in the melted butter and the egg yolk. Stir gently until the mixture is fully combined and crumbly.
Reserve Topping: Remove 1 cup of this oat mixture and place it in a small bowl. Mix it with the extra 1 tablespoon of brown sugar. Set aside for the topping.
Press the Crust: Press the remaining oat mixture firmly and evenly into the bottom of the prepared 8×8 pan.
Prep Berries: In a separate bowl, gently toss the blueberries, lemon juice, granulated sugar, and cornstarch together until the berries are well coated.
Assemble: Spoon the blueberry mixture evenly over the pressed oatmeal crust.
Add Crumble: Sprinkle the reserved 1 cup of oat topping evenly over the blueberries. Squeeze the topping in your hand slightly to form nice, chunky crumbles.
Bake: Bake for 45 to 55 minutes, or until the top is golden brown and the berry filling is bubbling. (If using frozen berries, bake for 50-60 minutes).
Cool & Slice: Let the bars cool completely in the pan for at least 3 hours. Use the parchment overhang to lift them out before slicing. Enjoy!

Find it online: https://www.endrecipes.com/blueberry-oatmeal-crumble-bars/