Step 1

Preheat oven to 375 F. Grease a 9-inch square baking pan with cooking oil spray.

Step 2

In a large mixing bowl, combine blueberries, lemon juice, flour, and sugar. Gently toss to combine. Evenly distribute the blueberry mixture into the greased pan.

Step 3

In another mixing bowl, combine softened butter, oats, flour, sugar, and cinnamon. Stir together with a rubber spatula until combined. Evenly distribute the topping on top of the blueberry layer.

Step 4

Bake for 35 to 40 minutes until the top is lightly browned. Place on a wire cooling rack to cool down for 10 minutes, then serve warm with whipping cream or a scoop of vanilla ice cream.