In a large ovenproof skillet, cook the bacon until crisp. Transfer the bacon to a paper towel and set aside.
Drain all but 3 tablespoons of bacon grease. Add the onions and mushrooms to the skillet and saute` over medium heat until softened but not browned, add potato slices and gently toss them in with the onions and mushrooms. Cook, turning often until potatoes are warmed through.
In a medium bowl add eggs, milk, parsley and cheese. Season with salt and pepper, stir until all is combined, pour mixture over the potatoes and sprinkle crumbled bacon on top.
Place skillet into the oven and bake until eggs are set about 25 - 30 minutes. Serve hot directly from the skillet.