Combine onion, wine, soy sauce, olive oil, garlic, mustard, and ginger.
Pour cups of water into the dish; add the steak and coat well.
Pour the remaining marinade into the dish; add peppers and onion.
Refrigerate both for 3 hours, turning occasionally.
Drain marinade from steak. Lightly oil grill rack.
Cook the steak on the grill for 4-5 minutes on each side.
Drain marinade from vegetables. Grill in the basket.
Brush rolls with pepper, oil, and garlic mixture.
Grill cut side down for 2-3 minutes.
Slice the steak thinly and put it on the bottom part of the bun.
Cover the steak with the vegetables and the top part of the bun. Serve as soon as possible.