Combine the presliced mushrooms, wine, and steak in a large zip-top plastic bag, and seal. Marinate in the refrigerator for 30 minutes, turning occasionally.
Remove the steak from bag, reserving marinade. Place a large nonstick skillet coated with cooking spray over medium-high heat. Add steak; cook for 6 minutes or until desired degree of doneness, turning after 3 minutes. Remove from pan.
Combine the onions, 2 tablespoons parsley, rosemary, and remaining ingredients. Add onion mixture and reserved marinade to pan. Bring to a boil; cook until reduced to 2 cups (about 15 minutes), stirring frequently.
Cut the beef diagonally across grain into thin slices. Place beef on a serving platter. Spoon the mushroom sauce over beef. Sprinkle with 2 tablespoons parsley.