Peel apples and quinces, core them and cut them in thin slices - You can use an apple slicer for the apples, but make sure the quince is cut as thin as possible. Add all ingredients to a large pot, and bring to a boil. Cover the pot, reduce heat to medium-low, and simmer until the fruit is tender (about 20-30 minutes), stirring occasionally.
Pour the fruit mixture from the pot into a mixing bowl, and slowly sift in the sweet rice flour, making sure to mix it in evenly so there are no lumps.
Pour fruit mixture into a partially pre-baked pie crust. Use your fingers to crumble the streusel topping across the entire top of the pie. Arrange small pieces of margarine across the top, and bake for 20-20 minutes, or until the topping is golden-brown and the filling is bubbling. Remove from oven and allow to cool before serving.
In a food processor with blade attachment, process pecans until they are in nearly uniform small chunks. If you have a plastic blade or mixer attachment, attach it and add the rest of the ingredients. If you only have a metal blade, pulse ingredients as slowly and minimally as possible.
Process only until ingredients are well combined and form a uniform, crumbly mixture. Use your fingers to crumble it into small pieces over the top of a pie, fruit crisp, muffins, or other baked good. Place dish into a preheated oven at 400°F Bake until the crumble topping is browned but not burnt (watch carefully to make sure the top doesn't char), approximately 20 minutes.