Using precooked chicken sausage cuts way down on prep time. Plus, there are so many varieties available to add layers of flavor. Italian, apple-flavored or breakfast-style varieties all pair well with the spinach in this quiche.
Preheat oven to 375°F. Set out pie crust to thaw for 10 to 20 minutes.
Meanwhile, heat oil in a large nonstick skillet over medium heat. Add chicken sausage and cook, stirring occasionally, until golden brown, about 4 minutes. Transfer to a plate. Add spinach to the pan and cook until it's just wilted; 1 minute. Spread the sausage and spinach in the bottom of the crust.
Whisk eggs, milk, salt and pepper together in a medium bowl. Pour the mixture over the sausage and spinach in the crust.
Set the quiche on a baking sheet and bake until the center is set, 35 to 40 minutes. Let stand for 10 minutes before slicing.