In a small saucepan, bring rice and water to a boil. Reduce heat; simmer, covered, until rice is tender, 35-40 minutes., Preheat oven to 350°. Place beans, corn, tomatoes, cheddar cheese and rice in a large bowl; stir in salsa, sour cream and pepper. Transfer to a shallow 2-1/2-qt. baking dish coated with cooking spray. Sprinkle with onion and olives. , Bake, uncovered, 30 minutes. Sprinkle with Mexican cheese; bake, uncovered, until heated through and cheese is melted, 5-10 minutes. Let stand 10 minutes before serving.