Heat oil in large skillet over medium-high heat until hot. Add onion; cook 3 to 4 minutes or until crisp-tender, stirring frequently.
Add rice, bell pepper, meatballs, olives and water. Bring to a boil. Reduce heat; cover and simmer 20 minutes, stirring once halfway through cooking.
Stir in zucchini and tomatoes. Cover; cook an additional 8 to 10 minutes or until zucchini is tender and liquid is absorbed, stirring occasionally. Sprinkle with cheese.