Cook broccoli according to package directions; drain well. In a large saucepan, combine the soup, sour cream, garlic salt, 1 c cheese and 1 1/4 cups onions. Cook over medium heat for 4-5 minutes or until heated through. Stir in the broccoli.
Pour into a grease 2-qt baking dish. Bake, uncovered, at 325 for 25-30 minutes or until bubbly. Sprinkle with the remaining cheese and onions. Bake 10-15 minutes longer or until cheese is melted.