Cream butter in a mixing bowl. Gradually add 1 cup sugar; beat well. Add yolks and flour; mix well. Fold in peaches. Pour mixture into pastry shell. Bake at 350° for 40 minutes.
Beat egg whites (at room temperature) until foamy. Add 1/2 cup sugar, 1 tablespoon at a time, beating until stiff peaks form. Spread meringue over filling; seal to edge of pastry. Bake at 350° for 8 minutes or until golden brown. Cool and refrigerate.