Preheat oven to 375 degrees F.
Whisk together eggs, milk, heavy cream, salt and pepper.
Lightly coat 12-cup muffin pan with a nonstick spray.
On a lightly floured surface, roll out the pie crust to slightly less than ⅛ inch thick. Use a 3¼-inch round cutter to cut out 12 rounds.
Fit a round into each muffin cup.
Divide the onions, bacon and cheese evenly between the pastry-lined cups.
Divide the egg mixture evenly between cups, filling no higher than the pastry (there may be leftover egg mixture).
Bake for about 25 to 30 minutes, or until quiches are golden and puffy.
Serve quiches hot or at room temperature.