Spray inside of slow cooker with no stick cooking spray. Mix Gravy Mixes and water in slow cooker until well blended. Add broccoli; stir to blend well. Cover.
Cook 1 hour on HIGH. Uncover and stir. Cover again.
Cook 2 hours longer on HIGH or until broccoli is tender. Uncover and stir. Sprinkle with cheese. Top with onions. Cook, uncovered, 10 minutes longer on HIGH or until cheese is melted.