Thaw pie shell, then bake in a 425 degrees oven until light brown (about 5 minutes). Cool on wire rack. Reduce oven temperature to 350 degrees. Sprinkle cheese, bacon and onion into pie shell. Beat eggs, milk and salt until well blended. Pour over cheese, bacon and onion mixture. Bake 30 to 35 minutes until a knife inserted halfway between center and edge comes out clean. Let stand for 5 minutes before cutting. Refrigerate any leftover quiche.