Heat oven to 375°.
Whisk dry ingredients together, then cut the butter in with a fork. Whisk up the egg and add to the mixture.
Reserve 1/3 of the crust mixture. Press 2/3 of the crust mixture into a 9" x 13" baking pan. Bake 10 minutes.
While the crust is baking, mix the brown sugar into the reserved crust.
Stir together all the ingredients for the blueberry filling.
Pour blueberry filling onto partially baked crust.
Drop the cookie crumble topping onto blueberry layer with a tablespoon.
Bake another 25 to 35 minutes.