Slow Cooker Method: Omit oil. Mix beef, onion, broth, undrained tomatoes, mushrooms, carrots, 1/2 cup water, oregano, garlic powder, thyme, pepper and bay leaf in slow cooker. Cover. Cook 7 to 8 hours on LOW or 4 to 4 1/2 hours on HIGH. Mix cornstarch and 4 teaspoons cold water. Stir into beef mixture along with rice. If using LOW setting, turn to HIGH. Cover and cook 30 minutes longer. Discard bay leaf.