Spray the insides and rim of the jars and place them on a baking sheet.
In a medium bowl, combine all of the ingredients for the filling. Spoon the filling into the jars, using the back of a mixing spoon to press blueberries down if needed to allow about ½ inch for the topping. Note: the filling will compress when cooking.
In a separate bowl, combine all of the ingredients for the topping. Spoon the topping evenly across the four jars, distributing across to the top of the filling to cover it.
Place baking sheet with jars in the preheated oven and bake for 30 minutes or until the filling is bubbly and the tops are lightly golden in color.
+If making these Gluten-Free, please ensure the ingredients tagged with the ‘+’ are gluten-free.