Preheat the oven to 375 degrees F.
In a large skillet over medium heat, add the bacon and cook until crisp. Remove from pan and drain on a brown paper bag or paper towels and reserve the fat in the pan. Chop the bacon when cooled and reserve.
To the same skillet with reserved bacon fat, add the onions and mushroom stems and cook until the onions are translucent and the mushrooms are browned, about 5 minutes.
In a large bowl mix together the eggs, milk, herbs and salt and pepper, to taste. Stir in the cheese, the reserved bacon and the mushroom mixture.
Pour the filling into the pie crust. Put on a baking sheet and bake until the quiche has set and top and crust has browned, about 30 to 35 minutes.