Preheat oven to 375°F.
Heat the olive oil in a skillet and add the onion, green pepper, garlic, celery, and mushrooms. Cook over medium-low heat, stirring often, for 5 minutes.
Transfer to a lightly oiled 2 quart casserole. Add the tomatoes, rice, salt, and pepper. Pour in the broth, stir, cover, and bake 30 minutes. Stir again and bake for another 30 minutes.
Prep Time: 10 mins.
Cook Time: 65 mins.