How to Make It
For the crust, preheat oven to 375°.
Combine quinoa, pepper, and egg in a bowl, stirring well. Press mixture into bottom and up sides of a 9-inch pie plate coated with cooking spray. Bake at 375° for 20 minutes; cool.
For the filling, heat a nonstick skillet over medium heat. Add oil and onion; sauté 3 minutes. Add spinach; sauté 3 minutes. Remove from heat; cool.
Combine milk and next 5 ingredients in a bowl; stir with a whisk. Arrange spinach mixture in crust; pour egg mixture over spinach. Sprinkle with feta. Bake at 375° for 35 minutes. Let stand 5 minutes; cut into 4 wedges.