Preheat oven to 350degrees. In a small skillet, heat oil over medium heat. Add onion; cook and stir until tender. In a large bowl, whisk eggs and condensed soup until blended. Stir in vegetables, bread crumbs, basil, salt and onion. Transfer mixture to an 11x7-in. baking dish coated with cooking spray., Bake, uncovered, 40-45 minutes or until bubbly. Sprinkle with cheese. Bake 5-10 minutes longer or until cheese is melted. Let stand 10 minutes before serving. If desired, sprinkle with additional basil.