Combine soya sauce, wine, oil and ginger or garlic in a shallow bowl. Score meat with shallow cuts, criss-cross-style at 2-inch intervals and add to marinade, turning to coat meat. Cover and refrigerate for at least four hours but preferably overnight, turning occasionally.
Remove meat from bowl, reserving marinade. Barbecue over medium-hot coals or at medium-high setting, brushing occasionally with marinade, 4 to 6 minutes per side, or until cooked to desired doneness.
Remove from barbecue and let stand for 5 minutes, then cut diagonally across the grain, in extra-thin slices. Wrap well and chill.