Heat oven to 425°F. Unroll 1 pie crust on work surface. Sprinkle both sides lightly with flour; place in ungreased 9-inch deep-dish glass pie plate. Press firmly against side and bottom.
In 4-quart saucepan, place all filling ingredients except 1/4 cup flour. Cook over medium heat, stirring frequently, 10 minutes or until grapes are tender. Stir in flour. Set aside.
In medium bowl, mix all topping ingredients except egg until crumbly. Spoon 2/3 of topping into crust-lined plate. Spoon filling over topping.
To make lattice top, cut second crust into 1/2-inch-wide strips with pastry cutter. Place half of the strips across filling in pie plate. Weave remaining strips with first strips to form lattice. Trim ends of strips even with edge of bottom crust. Fold trimmed edge of bottom crust over ends of strips, forming a high stand-up rim. Seal and flute. Brush lattice strips with egg. Sprinkle remaining 1/3 of topping over pie. Place sheet of foil over pie to prevent excessive browning; bake 20 minutes. Remove foil; bake 15 to 20 minutes longer or until topping is golden brown. Cool at least 2 hours before serving.