Drain pineapple, reserving 1/2 cup juice; set aside. In a large bowl, combine the mayonnaise, salt, pepper, mustard, and reserved pineapple juice; mix well. Fold in rice, ham, green pepper, 1 cup cheese, onion and pineapple.
Transfer to a greased 2-quart baking dish. Cover and bake at 350 for 30 minutes. Sprinkle with remaining cheese. Bake, uncovered, for 10 minutes or until heated through and the cheese is melted.