Let the dough sit at room temperature for 10 minutes before rolling.
Preheat the oven to 400F/200C
Roll out the crust on a lightly floured surface to about ¼ inch thick. Transfer it to a 9" pie pan. Trim the edge or crimp if desired. Prick the bottom with a fork.
Cover the crust with baking paper and fill with baking beads. Blind bake for 10 minutes. Remove the paper and baking beads and set the crust aside.
For the filling:
In a large bowl, combine the sugars, flour and orange zest. Add the eggs and whisk until smooth. Gently stir in rhubarb and strawberries. Add the filling to the pie crust.
For the topping:
Add all of the ingredients to a food processor and pulse until combined.
Squeeze to form lumps and crumble over the pie.
Bake for 45-50 minutes (covering with foil if it starts looking too brown). Cool on a wire rack for at least 30 minutes before serving.