Vegetarian Mushroom Cheesesteak with Caramelized Onions

Name: Vegetarian Mushroom Cheesesteak with Caramelized Onions
Prep time: 10 min
Cook time: 50 min
Total time: 1 h
Cuisine: American
Ingredients: 2 tablespoons olive oil (divided); 2 large onions (white, yellow, and red all work; 3 small onions); 1/2 teaspoon salt; 16 ounces baby bella or white mushrooms (thickly sliced); 1 red bell pepper, sliced (sliced); 1 green bell pepper (sliced); 1 tablespoon soy sauce; 1 tablespoon all-purpose flour; 1 teaspoon dry oregano; 4 6" sub rolls; 4 slices provolone cheese