Stir together first 7 ingredients in a large bowl, stirring just until combined. Spoon into a lightly greased 13 x 9 inch baking dish.
Roll 1 piecrust to fit baking dish; place on berry mixture. Cut remaining piecrust into 1/2 inch strips. Arrange strips in a lattice design over other piecrust. Brush with egg, and lightly sprinkle with 1 tablespoon sugar.
Bake at 400F for 55-60 minutes or until golden and bubbly.