Combine soy, garlic, ginger, brown sugar, lemon juice, oil, onion, and pepper.
Pour over steak, cover, and refrigerate for 6 hours or until next day.
Lift steak from marinade and drain briefly (reserve marinade).
Place on lightly greased grill 4 to 6 inches above a solid bed of glowing coals.
Cook, turning once and basting with reserved marinade, for about 6 minutes on each side or until done to your liking when slashed.