Spray 8-inch square pan with cooking spray. In 2-quart saucepan, heat milk and salt to boiling. Gradually add grits, stirring constantly; reduce heat. Simmer uncovered about 5 minutes, stirring frequently, until thickened. Add cheese, bacon, onions and pepper; stir until cheese is melted. Spoon mixture into pan. Refrigerate at least 4 hours or up to 24 hours.