Roll thawed sheet of puff pastry to a 10 x 7-inch rectangle; cut off one-third lengthwise. Place larger piece on baking sheet; prick with fork. Cut smaller piece lengthwise into 3/4-inch-wide strips. brush borders of larger piece with egg. Place strips on borders; brush with egg.
Mix apples, cut in 1/8-inch slices; lemon juice; and sugar. Place mixture in prepared pastry. Overlap slices in 2 lines down length.
Bake at 375°F for 30 minutes. Glaze with melted jelly.