1. Prepare the pastry: Roll out one pie pastry disk to an 11-inch circle. Fit it into a 9-inch pie plate, pressing firmly into the sides and bottom. Roll out the second disk and cut it into strips for a lattice top (or keep it whole for a full top crust). Refrigerate the top crust until needed.
2. Macerate the fruit: Dice the peaches and place them in a large bowl. Add the sugar, quick cooking tapioca, orange zest, orange juice, vanilla extract, nutmeg, and salt. Let the mixture sit for 10 minutes to allow the fruit to release its juices and the tapioca to soften.
3. Add the blueberries: Gently fold the fresh blueberries into the macerated peach mixture. Adding them last prevents their delicate skins from bursting.
4. Fill the crust: Pour the fruit filling and all accumulated juices into the prepared bottom crust. Arrange the fruit to eliminate gaps and lightly press down to compact the mixture.
5. Assemble the top crust: Place the lattice or full top crust over the filling. Trim the edges and crimp the top and bottom crusts together securely. If using a full crust, cut several slits to allow steam to escape.
6. Bake the pie: Preheat the oven to 425°F (220°C) and place racks in the lowest and middle positions. Place the pie on a rimmed baking sheet on the lowest rack. Bake for 25 minutes.
7. Finish baking: Lower the oven temperature to 400°F (200°C). Cover the edges with aluminum foil if they are browning too quickly. Continue baking for 35 to 40 minutes, until the juices bubble vigorously and an instant-read thermometer inserted into the center reads above 200°F (93°C).
8. Cool completely: Transfer the pie to a wire rack. Allow it to cool at room temperature for at least 6 hours before slicing. This crucial step allows the tapioca to fully activate and the juices to set into a sliceable consistency.