Heat oven to 350°F. Spray 13x9-inch (3-quart) baking dish with nonstick cooking spray. Cook broccoli as directed on package for minimum cooking time.
Meanwhile, in large bowl, combine soups, mayonnaise, mustard and pepper; mix well.
Drain broccoli; arrange in sprayed baking dish. Add turkey; toss gently. Pour soup mixture over top, spreading evenly over broccoli and turkey. Sprinkle with cheese.
Bake at 350°F. for 30 minutes or until hot and bubbly. Sprinkle with onions; bake an additional 5 minutes or until onions are lightly browned.