Preheat oven to 425. Line pie pan with pie crust and crimp edges. Sprinkle the bottom with onion, bacon and then cheese. Slightly beat eggs and combine with remaining ingredients. Pour into pie shell. Bake 15 minutes. Do not remove from oven but lower oven temp to 300. Bake an additional 30 minutes or until knife comes out clean 1 inch from edge. Let stand 10 minutes before cutting.
For variations, substitute other cheeses and add vegetables such as spinach, mushrooms, brocolli or seafood, such as crabmeat or shrimp.