Preheat oven to 350. Wash and remove stems from mushrooms. Chop stems finely and set aside. Heat margarine or oil in a medium-sized skillet. Add mushroom stems, onions and green peppers. Cook until tender. Remove from heat and add crab meat. Stuff mushroom caps with this mixture and place on an ungreased baking dish. Combine cheese, pepper flakes, basil, pepper and garlic in a small bowl. Sprinkle over mushrooms. Bake for 20 minutes or until thoroughly cooked.