Preheat oven to 350°F. Grease a 9 ½ inch deep dish pie plate or similar sized baking dish. Set aside.
Filling:
In a large bowl, combine all filling ingredients. Stir gently until well combined. Dump into prepared baking dish and spread into an even layer.
Topping:
In a large bowl, combine oats, flour, sugars, salt and cinnamon. Add melted butter and stir until well combined (I use a fork). Sprinkle the topping over the blueberries (pressing some of it together with your fingers to form clumps).
Bake for 30-40 minutes until the fruit is bubbling and juicy and the topping is light golden brown. Cool slightly, serve warm with vanilla ice cream.
Notes
*You can use fresh or frozen blueberries. Fresh blueberries will hold their shape better after baking.