Recipe Arizona Chicken

Ingredients
6 boneless skinless chicken breast halves (1-1/2 pounds)
1/4 cup vegetable oil, divided
1 medium onion, sliced
4 cups chopped fresh tomatoes
2 celery ribs, sliced
1/4 cup water
1/4 cup sliced stuffed olives
2 teaspoons garlic powder
2 teaspoons dried oregano
1 teaspoon salt
1/4 teaspoon pepper
1/2 pound fresh mushrooms, sliced

Directions
In a skillet, brown chicken on both sides in 2 tablespoons of oil. Remove and set aside. In the same skillet, saute onion in remaining oil until tender. Add tomatoes, celery, water, olives, garlic powder, oregano, salt if desired and pepper; bring to a boil. Cover and simmer for 15 minutes. Return chicken to pan. Simmer, uncovered, for 15 minutes. Add mushrooms; simmer 15 minutes longer or until meat juices run clear.