Mix together ground beef, ground pork, egg, brown rice, half of the onions and thyme in a large bowl; form into small balls. Coat a large, heavy-bottomed saucepan with vegetable cooking spray and brown meatballs, about 5 to 10 minutes.
Add water, tomato, chili powder, garlic and remaining onions; simmer for 35 minutes. Add carrots, celery and peas. Simmer for 10 minutes or until vegetables are tender. Serve hot.Servings: 4