In a large saucepan, bring rice and water to a boil. Reduce heat; cover and simmer for 35-40 minutes or until tender.
In a large bowl, combine the beans, Mexicorn, tomatoes, salsa, sour cream, cheddar cheese, pepper and rice. Transfer to a shallow 2-1/2-qt. baking dish coated with cooking spray. Sprinkle with onion and olives.
Bake, uncovered, at 350° for 30 minutes. Sprinkle with Mexican cheese. Bake 5-10 minutes longer or until heated through and cheese is melted. Let stand for 10 minutes before serving.