Preheat the oven to 375℉. Fit the pie crust into a 9″ pie plate and crimp edges.
In medium-size bowl, whisk together the eggs, milk, salt and pepper.
Spread spinach over the bottom of the prepared pie crust. Pour the egg mixture evenly over the spinach, and then sprinkle with the cheese.
Bake the quiche at 375℉ for 15 minutes. Reduce the heat to 325℉ and continue to bake 20 more minutes, or until puffed and the crust is browned.
Remove from the oven and let stand 5 minutes before slicing and serving.