Beat together the cheese, yogurt, green onion, and parsley; set aside.
Saute onion in half the margarine until limp.
Add mushrooms and remaining margarine and saute just until hot through; set aside.
Shape meat into 4 patties and place on a broiling rack.
Season with salt and pepper and broil, turning to brown both sides, and cooking until medium rare.
Spoon mushrooms over each patty and top with a dollop of cheese dressing.
Return to the broiler just until cheese browns lightly.
Contains about 310 calories per serving.