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Three blueberry crumb bars in a stack.

Blueberry Crumb Bars⁣

Blueberry crumb bars with a crunch oat crust and topping. Use fresh or frozen blueberries. Both work great in this recipe. Be sure to let the bars cool before cutting. They’re really delicate when they first come out of the oven.
Prep Time 15 minutes
Cook Time 45 minutes
Total Time 1 hour
Servings 12 bars

Ingredients

For the Oat Crust and Topping

  • 1 ½ cups old-fashioned rolled oats (4 ounces⁣; 113 grams)
  • 1 cup all-purpose flour (5 ounces⁣; 142 grams)
  • ½ cup brown sugar (3 ½ ounces⁣; 100 grams)
  • 1 teaspoon ground cinnamon⁣
  • ¼ teaspoon salt⁣
  • ½ cup butter, soft (4 ounces; 113 grams)

For the Blueberry Filling

  • 2 cups blueberries, see note (1 pint⁣)
  • ¼ cup granulated sugar (1 ¾ ounces⁣; 50 grams)
  • 1 tablespoon cornstarch⁣
  • Finely grated zest of 1 medium lemon⁣
  • Juice of 1 lemon about 2 tablespoons⁣

Instructions

Make the Oat Crust/Topping

  1. Preheat the oven to 350°F. Line an 8-inch square baking dish with parchment paper or aluminum foil, leaving a little overhang on all sides. (If you’re using parchment paper, you can clip it to the pan with binder clips. This holds it in place.) Grease the parchment or foil lightly with cooking spray; set aside.⁣

  2. Place the oats, flour, brown sugar, cinnamon, and salt in a large bowl. Stir to combine. ⁣Break up any piece of brown sugar with your hands or a fork.

  3. Add the butter. Mix the butter into the oat mixture with a pastry cutter or your fingertips. The mixture should be crumbly and hold together when squeezed.⁣

  4. Set aside 1 cup of the oat mixture in a small bowl. Press the remaining mixture into the bottom of the prepared pan. Be sure to press it firmly down.

Make the Filling.

  1. Place the blueberries in a medium bowl. Add the sugar, cornstarch, lemon zest and lemon juice and toss gently to combine. Spread the blueberries over the crust. Sprinkle the reserved crumb mixture over the blueberries. (Remove binder clips from pan now. They aren’t oven-safe.)⁣

Bake the Bars

  1. Bake until the filling is bubbling and the top is golden-brown, about 45 minutes. Let cool at least 2 hours before cutting into bars.⁣

  2. Store the bars covered in the refrigerator for up to four days or allow to cool and freeze for up to three months.⁣

Recipe Notes

Blueberries. 

Use fresh or frozen blueberries. If you're using frozen blueberries, don't allow them to thaw being using. 

For extra filling, increase the blueberries in the filling to three cups.