Heat olive oil in a lg saucepan, add onion and saute 1 minute. Add garlic and saute 1 minute more. Add rice and stir to coat, add broth and bring to a boil. stir in spinach, mushrooms, tomatoes, and 1/4 cup of the cheese. Por into oiled casserole dish, top with remaining cheese, cover and bake 40 minutes or until most of the liquid is gone and rice is tender.