Place rolled oats in a food processor or blender and pulse until a coarse flour is created.
Mix together the oat flour with the whole wheat flour and salt. Add the coconut oil in small pieces at a time.
Blend with a pastry cutter or hands or pulse in the food processor until pea-like crumbles are in the crust. Add the water in small amounts until the dough is the right consistency: Dough should be pretty shaggy and dry but come together when pinched between the forefinger and thumb.
Form the dough into a ball. Wrap tightly in plastic wrap and refrigerate for 30 minutes and up to 24 hours. Don't worry if the dough is shaggy, it will come together more after refrigeration. Roll dough out onto a floured work surface. Place the quiche/pie pan on top of the dough, upside down, and cut a circle. Carefully turn over and press the dough into the pie pan and trim the edges.
Use a fork to crimp the outer edges of the crust or use fingers and fold over edges. Add the quiche mixture (recipe below).
For the Quiche Filling
Heat onion and garlic in a skillet with olive oil for about 5 minutes, until onion is softened and translucent. Add spinach and cook, just until wilted. Remove from heat. Mix in sun-dried tomatoes.
Meanwhile, beat/whisk egg whites until very frothy. Whisk whole eggs in a separate bowl. Combine the eggs and whites. Add parmesan cheese, salt, and pepper. Fold in the spinach tomato mixture and pour into the pie shell. Bake for 25 minutes or until set in the center and golden at the edges.
If desired, sprinkle with walnut pieces 5 minutes before removing from the oven.