Let the pie crusts stand at room temperature for 15 to 20 minutes. Preheat the oven to 375 degrees. Spray 48 miniature muffin cups with non-stick cooking spray.
Open and unfold one pie crust, then press out any fold lines. With a 2-½ inch biscuit cutter, cut out 12 rounds. Repeat with remaining 3 pie crusts.
In the prepared mini muffin tins, press 1 round of pie crust into the bottom and up the sides of the cup. In a 4-cup measuring cup, combine the eggs, milk, and the salt. Whisk well. Set aside.
Mini Bacon Quiche
In 12 of the mini muffin cups, add 1 tablespoon of cheese. Evenly divide the chopped bacon among the 12 cups, using about ½ teaspoon bacon in each. Top with a couple slices of green onion.
Mini Ham And Cheese Quiche
In 12 of the mini muffin cups, add 1 tablespoon of cheese. Evenly divide the chopped ham among the 12 cups, using about ½ teaspoon ham in each.
Mini Spinach Quiche
In 12 of the mini muffin cups, add 1 tablespoon of cheese. Evenly divide the wilted spinach among the 12 cups, using about about ½ teaspoon spinach in each. Evenly divide the chopped red pepper among the mini muffin cups.
Mini Mushroom Quiche
In 12 of the mini muffin cups, add 1 tablespoon of cheese. Evenly divide the chopped mushroom among the 12 cups, using about ½ teaspoon mushroom in each.
Finish And Bake
Pour egg mixture into each of the 48 cups, filling to within ¼ inch of the top. Bake at 375 degrees until golden brown, about 25 to 30 minutes. Cool slightly and serve warm.