Vegetable Beef Casserole

In a 3-qt. casserole dish, layer half each potatoes, carrots, celery, green beans and onion. Crumble half the uncooked beef over vegetables. Sprinkle with 1/2 teaspoon each thyme, salt and pepper. Repeat layers. , Top with tomatoes. Cover and bake at 400° for 15 minutes. Reduce heat to 350°; bake about 1 hour longer or until vegetables are tender and meat is no longer pink. Sprinkle with cheese; cover and let stand until cheese is melted.