Heat oil in a large skillet over medium heat. Add onion and garlic; cook for 5 minutes or until onion is softened. Stir in cumin; cook for 2 minutes. Add beef, breaking up with a wooden spoon; cook for 5 minutes. Add tomato sauce, Worcestershire sauce, black pepper, ketchup, horseradish and salt, if using. Cook for 6 minutes. Remove from heat. Stir in cooked rice and Cheddar cheese. Spoon into green pepper shells, dividing equally. Top with parsley. Place the peppers in a 9 x 9 x 2-inch baking pan.