Heat olive oil in large skillet over medium heat. Add mushrooms and onions; cook, stirring frequently, for 5 to 7 minutes or until most of the mushroom liquid has evaporated and onions are translucent. Remove from heat. Stir in roasted peppers. Let cool slightly.
Combine cooked vegetables, provolone cheese, salt and pepper in large bowl. Sprinkle mixture into pie shell.
Whisk together evaporated milk and flour in large bowl until lumps of flour are gone. Whisk in eggs and season with black pepper, if desired. Pour milk mixture over vegetable and cheese mixture. Sprinkle with feta cheese and green onions.
Bake for 50 minutes or until golden brown and knife inserted near center comes out clean. Cool for 10 minutes before serving.
Notes/Tips/Substitutions: 1) Larger portabella mushrooms can be used if baby bella or cremini mushrooms are not available. Cut into smaller pieces prior to cooking with onions. 2) Consider substituting goat cheese for Feta cheese. Fontina cheese can be used instead of provolone cheese. 3) Other vegetables such as chopped artichoke hearts or chopped sundried tomatoes can be added.