Place extra virgin olive oil in skillet, add bell pepper. onions and garlic salt. Stir occasionally until peppers and onions begin to soften (3-5 minutes). Add mushrooms and continue cooking until mushrooms are softened (3-5 minutes), stir occasionally. Place sautéed veggies on 4 slices of Milton's Healthy Multi-Grain Bread and top with mozzarella cheese. Heat broiler. Place bread slices on broiler pan. Broil for 2 minutes or until cheese is melted. Take out of the broiler and top with the remaining 4 slices of bread. Cut sandwich in half and serve.