Heat the oil in a medium saucepan and sauté the onions for 10 minutes. Add the celery and mushrooms. Sauté another 5 minutes over a medium-low flame. Remove from the flame.
Note: If using whole barley, soak overnight or 6 to 8 hours and simmer in the soaking water for about 1 hour before combining with rice.
Heat up a skillet and dry roast the rice and barley over a high flame until most of the water from washing the grain has evaporated. Reduce the flame to medium-low and dry roast 3 to 4 minutes longer. Place in a baking dish. Add the onions, celery and mushrooms. Bring the water to a boil and pour over the rice. Mix in the salt, pepper and thyme. Cover the baking dish and bake for 1 hour at 350° until the grain is tender. Remove and mix in the parsley. Serve.
Per serving - 305 calories, 7 g fat (19% calories from fat), 12 g protein, 53 g carbohydrate, 9 g fiber, 0 mg cholesterol, 107 mg sodium