Heat oven to 450°F. Remove pie crusts from pouches. Unroll and stack crusts one on top of the other on lightly floured surface. Roll to 17x12-inch rectangle. Fit crust into 15x10x1-inch pan, pressing into corners. Fold extra pastry crust under, even with edges of pan. Crimp edges.
Mix granulated sugar, flour, cinnamon, nutmeg, salt and lemon juice. Stir in apples to coat. Spoon apple mixture into crust-lined pan.
Bake 33 to 38 minutes or until crust is golden brown and filling is bubbling. Cool on rack 45 minutes.
Mix powdered sugar and milk until well blended. Drizzle over pie. Allow glaze to set before serving, about 30 minutes.