Use a shallow sided 9 inch glass pie plate or tart pan. Place the pie crust in the plate and crimp the edges. (We double folded the edges of the crust and then crimped them.) Prebake the crust for 10-12 minutes.
Allow to cool a bit, then place the spinach and cheese on the bottom of the pie crust.
In a medium bowl mix up the filling: milk, eggs, salt, pepper, garlic, onion powder. Pour over the spinach and cheese.
Bake for 45-50 minutes. Check if it's done by inserting a knife in the center. If it comes out clean, take the quiche out of the oven.
Let stand for 5-10 minutes before serving.