1. Cut stems from mushrooms; finely chop enough stems to measure 1/3 cup. Mix chopped mushroom stems, onion, celery and margarine in 1-quart casserole. Microwave uncovered on high (100%) until onion is tender, 2 to 3 minutes. Stir in bread crumbs, salt, marjoram, pepper and turmeric.
2. Fill mushroom caps with stuffing mixture; arrange mushrooms filled sides up (smallest mushrooms in center) on two 10-inch plates. Microwave one plate at a time uncovered on high (100%) 2 minutes; rotate plate 1/2 turn. Microwave until hot, 1 to 2 minutes longer.