1. Prepare rice as label directs.
2. Meanwhile, into 10-inch skillet, drain oil from tuna; set tuna aside. Heat oil over medium heat; add celery, green pepper, and onion, and cook about 3 minutes, stirring occasionally, until vegetables are tender-crisp.
3. When rice is done, add to vegetable mixture with tuna, peanuts, pimentos, and mushrooms with their liquid; heat through, stirring frequently.