Pre-heat oven 400 degrees.
In a quiche dish, line it with the frozen pie crust and press into the sides of dish. Add the onion slices being sure to break apart the rings. Be sure the onions are even on the bottom of the dish. Sprinkle the cheddar cheese and goat cheese evenly over the onions.
In a medium bowl, whisk the eggs until they are medium yellow color. Add the milk, herbs, mustard, Parmesan cheese, salt and pepper. Whisk to combine and pour over prepared crust. You may have to spread out the herbs if they have clumped together.
Place quiche in middle of oven and bake for 50 minutes or until it is puffed, browned and set in the center. Serve warm with a salad.