Mix together all of the pie filling ingrediets in a bowl let it sit while you mix up the streusel and roll out the pie crusts.
Mix together the oats, flour, brown sugar for the streusel and add the melted butter. Mix together until crumbly.
Roll out the pie crusts or use premade piecrusts and put bottom crust in the pie dish.
Add the pie filling to the pie dish.
Add the streusel and create the lattice top with the other pie crust.
Brush the top with the beaten egg and sprinkle with the sparkling sugar.
Bake at 400°F (204°C) for 20 minutes. Reduce the temperature to 350°F (176°C) and cover the edges with a pie edge protector and bake for another 45 minutes. Loosely tent with foil if crust is getting over browned.
Let the pie cool completely for about 3 hours prior to serving. The filling will set up and not be soft or runny when you serve.
Delicious with ice cream.
To freeze: Freeze the pie after it is baked. Thaw overnight in the fridge and serve at room temperature.
Keyword: fruit pie, rhubarb strawberry pie, strawberry rhubarb pie