Preheat oven to 425°F. Roll half of pastry into 12-inch circle; use to line 9-inch pie plate; set aside.
Combine sugar, corn starch and cinnamon in large bowl. Add peaches and lemon juice, if desired; toss to coat. Spoon into pie crust.
Roll remaining pastry into 12-inch circle; fit pastry loosely over filling. Trim overhang to 1 inch. Fold edges under; flute edge. Cut several 1/4-inch wide vents in top crust for steam to escape.
Bake 45 to 50 minutes or until fruit is tender and juices that bubble up in center are clear and shiny. If edge begins to overbrown, cover with strips of foil. Cool on wire rack.