Preheat the oven to 400F. Bake the pie crust for 5-7 minutes, until very lightly browned. Remove from oven and reduce oven to 325F.

Meanwhile, in a large saute pan, heat the oil over medium-high heat. Saute the mushrooms and onions for about 5 minutes. Add the spinach and saute until the spinach is wilted. If there is a lot of extra moisture in the pan, drain the vegetable mixture.

In a large bowl, stir together the eggs, milk, onion, bacon, spinach, mushrooms, and salt. In a separate bowl, toss the cheese and flour together. Add the cheese to the rest of the ingredients and mix well. Pour into your partially baked pie crust and bake 45-55 minutes, until set. Let it cool for about 20 minutes before slicing. It can be served warm or at room temperature