Prepare pie crust; bake at 375°F for 10 minutes.
Sprinkle Swiss/Gruyere cheese evenly on bottom.
Distribute cooked bacon strips over the top of the cheese.
Sprinkle onion evenly over the bacon and cheese.
Beat the eggs; add in the remaining ingredients and combine thoroughly.
Pour mixture over ingredients in pie pan in a circular motion. Place on a foil lined rimmed baking sheet.
Bake at 425°F for 15 minutes. Then, LOWER the oven temperature to 300°F and bake for an additional 30 minutes or until middle is set.
Allow it to stand at least 10 minutes on a cooling rack before slicing/serving.