Preheat oven to 325° F.
In blender of food processor, blend cheeses, onions, oil, seasonings, eggs and milk until smooth. Pour into bowl with spinach and blend well.
Grease a 9-inch pie plate. Pour in mixture. Bake 35-45 minutes or until knife inserted in center comes out clean. Let stand for 10 minutes before cutting.Servings: 4-6.