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Blueberry oat squares are sweet, buttery, and delicious, with three mouthwatering layers. With just 15 minutes of prep, they are the perfect treat. |

Blueberry Oat Squares

  • Author: Sam Hu | Ahead of Thyme
  • Total Time: 45 minutes
  • Yield: 9 squares
  • Diet: Vegetarian


Blueberry oat squares are sweet, buttery, and delicious, with three mouthwatering layers. With just 15 minutes of prep, they are the perfect treat.


For the crust:

  • 3/4 cup buttersoftened to room temperature
  • 1/2 cup brown sugar
  • 1 + 1/2 cups rolled oats
  • 3/4 cup all-purpose flour
  • 1 teaspoon vanilla extract
  • 1 teaspoon baking powder
  • pinch of salt

For the blueberry layer:

  • 2 cups blueberries, fresh or frozen
  • 3 tablespoons granulated sugar
  • 2 tablespoons lemon juice
  • 2 teaspoons cornstarch

For the oat topping:

  • 3 tablespoons buttermelted
  • 3/4 cup rolled oats
  • 1/4 cup brown sugar
  • 1 teaspoon ground cinnamon


  1. Preheat oven to 350 F.
  2. In a large bowl, use a hand mixer or stand mixer to cream together butter with brown sugar until light and fluffy. Add rolled oats, flour, vanilla, baking powder, and salt. Continue to mix until fully combined. The mixture will be slightly sticky. Transfer the mixture into a 9-inch square baking pan, and firmly press it in to create an even layer on the bottom. 
  3. In a large mixing bowl, add all the ingredients for the blueberry layer (blueberries, sugar, lemon juice, and cornstarch). Gently toss to combine. Evenly distribute the blueberry mixture over the crust.
  4. In a shallow saucepan, melt butter over medium heat. Once melted, remove from heat and stir in oats, sugar, and cinnamon. Stir until fully combined. Sprinkle and evenly distribute the topping on top of the blueberry layer.
  5. Bake for 30 to 35 minutes until lightly browned. Place on a wire cooling rack to cool down completely and cut into 9 even squares. Serve on its own or with a scoop of vanilla ice cream.


Wait before you slice: Feeling impatient? Don’t buy into your impulses. Wait for the blueberry oat squares to cool down completely before you cut them—or you could be looking at a drippy mess that ruins the square part of your oat squares.

How to store: If you have any leftover oat squares, store in a single layer in an airtight container (or layer them with parchment paper in between to prevent sticking). They will keep at room temperature for up to 1-2 days or in the refrigerator for up to 5 days.

How to freeze: Blueberry oat bars freeze really well and can be stored tightly wrapped in plastic cling wrap or in an airtight container for up to 3 months in the freezer. It's a great recipe to make a few batches of after a day of berry picking, freeze, and enjoy another day.

  • Prep Time: 15 minutes
  • Cook Time: 30 minutes
  • Category: Dessert
  • Method: Bake
  • Cuisine: American

Keywords: blueberry oat squares, blueberry oat bars, oat squares with blueberry filling, how to make blueberry oat squares, blueberry crisp squares