Brown the ground beef in the oil over high heat. Add chopped onions & reduce heat to medium; cook until tender. Stir in salt, pepper, garlic powder, thyme, oregano, bay leaf, crushed tomatoes, mushroom soup, and rice. Bring all to a boil; reduce heat and simmer 5 minutes, stirring occasionally. Discard bay leaf. Spoon into a 1 & 1/2 qt. casserole dish. Sprinkle cheese over top of the casserole. Broil just until cheese melts.