Preheat oven to 375 degrees. Using a sharp knife, core, peel, and slice peaches.
Place prepared peaches in large bowl. Sprinkle with flour and sugar. Add orange juice and blueberries. Gently stir until moistened.
In a small bowl, combine flour and salt. Cut in butter with pastry fork until crumbly. Add water and mix until combined. Mixture will form a ball. Roll out dough onto a lightly floured surface to 12x10" rectangle.
Transfer dough to a baking sheet lined with parchment paper or a silicone baking mat. Arrange fruit mixture down the center of crust, leaving a two-inch border. Fold edges of pastry over peaches. Brush pastry edges with 2 tablespoons milk and sprinkle with sugar. Bake for 25-30 minutes until pastry is golden brown. Serves 6-8.
Notes
*Unless otherwise indicated, all butter used on this recipe site is salted.