In 3-quart saucepan, cook ground beef over medium-high heat 5 to 7 minutes, stirring occasionally, until no longer pink; drain. Add onions and taco seasoning mix; cook 1 minute.
Stir in tomatoes, corn and water. Heat to boiling. Reduce heat; simmer 10 minutes.
To serve, ladle soup into serving bowls; top with cheese.
