Preheat oven to 400 degrees. Spray a glass pie pan with nonstick cooking spray.
Crack the eggs into a medium bowl. Beat lightly. Add the milk, stirring to mix together.
Sprinkle the ham over the bottom of the pie plate. Top with half of the cheese. Sprinkle the onions over the cheese.
Pour the egg mixture over the ham and cheese. Sprinkle with salt and pepper, then top with remaining cheese.
Bake the quiche for 20 minutes. Check to see if the quiche is done by inserting a knife into the center. If the knife comes out clean, the quiche is done. If the center is still soft and jiggly, return the quiche to the oven for a few more minutes. When the quiche is done, let it rest 5 minutes, then cut and serve.
You can add whatever you like to the egg filling. Leftover vegetables, meats, a baked potato and bacon. You can add herbs and or spices as you like.