Cook bacon until crisp. Drain the fat and dry the bacon bits on a paper towel lined plate.
If not using a pie crust, spray a pie plate with vegetable spray. In a large bowl, mix onion, chilies, Swiss cheese and bacon. Place the mixture in the pie crust or pie plate.
In a large bowl, beat together the eggs, half and half, salt, and pepper. Pour over the cheese mixture.
Bake for about 45 minutes. Let stand for an additional 10 minutes before cutting.