In a large bowl, combine blueberries, sugar, cornstarch, and cinnamon. Gently toss to coat.

In a separate bowl, combine flour, brown sugar, oats, and cinnamon. Cut in the cold butter using a pastry blender or your fingers until the mixture resembles coarse crumbs.

Preheat oven to 375°F (190°C). Place one pie crust in a pie plate. Pour the blueberry filling into the crust.

Sprinkle the crumble topping evenly over the blueberry filling.

Place the pie on a baking sheet and bake for 50-60 minutes, or until the crust is golden brown and the filling is bubbly.

Let the pie cool completely before serving. Enjoy!