Arrange fish with thickest parts to outside edge in microwavable dish, 10 x 6 x 2 inches.
Sprinkle with wine, salt and oregano.
Cover tightly and microwave on high 3 minutes; drain.
Sprinkle fish with bread crumbs and cheese; drizzle with margarine.
Rotate baking dish 1/2 turn.
Microwave uncovered on high until small ends of fish flake easily with fork, 2 to 4 minutes.
Let stand 3 minutes. (Fish will continue to cook while standing.)
Remove fish to platter.
Sprinkle with onion.