Preheat oven to 375 degrees F. In a medium skillet heat oil over medium heat. Add mushrooms and sweet pepper; cook for 5 to 8 minutes or until tender, stirring occasionally. Stir in tofu, green onion, garlic, and black pepper.
Place pita halves, cut sides down, on a baking sheet. Sprinkle with 1/4 cup of the cheese. Top with mushroom mixture. Sprinkle with the remaining 1/4 cup cheese. Bake for 8 to 10 minutes or until heated through and cheese is melted. Allow to cool. Cover and store in the refrigerator overnight. Reheat for 1 to 2 minutes in the microwave or 4 to 5 minutes in the toaster oven. If desired, serve with salsa.