Preheat oven to 375 F. Line a 9 x 13 baking dish with foil or parchment paper then spray with nonstick cooking spray. Set aside.

 In a medium bowl combine the filling ingredients, the 4 cups of blueberries, sugar, lemon juice and corn starch, and mix lightly. Set the blueberry mixture aside.

In a large bowl mix the dry ingredients, granulated sugar, brown sugar, baking powder , cinnamon and flour. Cut in the butter, egg and vanilla using a pastry cutter until the mixture resembles course crumbs.

Pat half the mixture into the bottom of the prepared pan in an even layer, then pour over the juicy blueberry filling. Top th blueberry layer with the remaining crumb mixture.

Bake for 45 minutes or until bars are golden brown. Bake time may vary depending upon your oven. Remove from oven, let cool then on a wire rack.