Brown chicken on both sides in hot oil in large frying pan; drain on absorbant paper; place in 3-quart baking dish and set aside. Saute rice in same frying pan, stirring often until golden brown. Add onion and garlic, saute 10 to 15 minutes until onion is tender. Drain and measure liquid from beans; add water to make 1 cup. Add liquid and beans to rice mixture. Stir in tomatoes, mushrooms, pimientos, parsley, salt, and pepper.
Bring mixture to boil, stirring often. Pour hot mixture over chicken in baking dish. Bake, convered in a 350 degree oven for approximately 1 hour, or until chicken and rice are tender.
(If necessary, add a little boiling water to moisten while baking.)