Place chopped onions and sliced squash in a 2-quart, heat- resistant, non-metallic casserole with water. Cover tightly and heat in Microwave Oven 7 minutes or until squash is tender. Drain excess water.
Soak crumbled slices of white bread in 1 cup mi1k, 5 minutes.
Add salt, monosodium glutamate, melted butter and grated cheese to bread and milk mixture. Stir to combine.
Pour bread and cheese mixture over squash and stir to mix together thoroughly.
Sprinkle top of mixture with Italian flavored dry bread crumbs. Cook, uncovered, in Microwave Oven 10 minutes or until cheese is melted. Variation: Zucchini may be substituted for yellow squash.