I made an oat flour crust for a dessert pie the other day, and it came out fine. I'm pretty sure I used the recipe from Bob's Red Mill. You won't get a flaky paté brisée without wheat flour, is all; once you give up on that idea you can make a crumb crust from just about any type of flour, including nut flours. GF oat flour is available, and I think the flavor would be fine for a quiche.