Preheat oven to 400 degrees F. Line a baking sheet with parchment paper; set aside. Let piecrust stand at room temperature according to package directions. Meanwhile, in a large bowl combine the flour, granulated sugar, and orange peel. Add peaches and orange juice; gently toss to coat; set aside.
Unroll piecrust on a lightly floured surface. Gently roll piecrust to a 12x10-inch rectangle, trimming as necessary. Transfer rectangle to prepared baking sheet. To make the scalloped edge, use a 2-inch round cutter to gently press circles around the edge of the dough, making sure not to cut all the way through the dough. Use a paring knife to cut around the outside circle edges to remove the scraps. Arrange peach slices in rows down the center of the crust, leaving about a 2-inch border. Spoon any remaining mixture from the bowl over the peaches. Sprinkle peaches with blueberries. Using the parchment paper to lift, fold up edges of pastry over peaches, pleating as necessary. In a small bowl combine egg and 1 tablespoon water; brush over pastry and sprinkle pastry with turbinado sugar.
Bake for 25 minutes or until pastry is golden and filling is bubbly (tart may leak a little as it bakes). Cool slightly and serve with ice cream, if desired.