Preheat the oven to 350 degrees F.
Finely chop both the onion and green pepper.
Add one stick of margarine and the chopped onion and green pepper to a large, Pyrex measuring cup (or similar microwave safe dish).
Microwave the margarine, onion and green pepper in one minute increments, stirring after each minute, until the margarine (or butter) is completely melted.
Drain two cans of mushrooms and add them to a large, clean bowl.
Add the rice, onion and green pepper mixture, and two cans of beef consommé.
Stir the mixture until well combined.
Carefully pour the rice mixture into a 9x13 casserole dish.
Bake the rice on the center rack of the oven at 350 degrees F, uncovered, for one hour.