Preheat oven to 350 degrees.
Lightly grease a 9-inch pie plate. Toss together bacon, cheese, onion and flour; spread on the bottom of the pie plate.
In a bowl, beat eggs together, then beat in milk, cayenne pepper and salt; pour over bacon mixture.
Bake, uncovered, for 35 to 40 minutes, or until a knife inserted in the center comes out clean. Let quiche stand for 10 minutes before cutting.