In a large mixing bowl, combine blueberries, granulated sugar, cornstarch, lemon juice and cinnamon. Stir carefully until blueberries are evenly covered then transfer to an 8" baking dish or divide into 5 ramekins.
With a fork, combine the oats, all-purpose flour, brown sugar, butter and cinnamon in a large bowl until crumbled. Sprinkle topping evenly over blueberries.
Bake 35-40 minutes or until the top is golden brown and blueberries are bubbling.
Cool 10 minutes and serve!
This recipe can be made in an 8" pan or divided into 5 smaller portions.