In shallow dish, whisk together soy sauce, oil, onion, garlic, ginger and pepper.
Add lamb, turning to coat; let stand for 10 minutes.
Reserving marinade, place lamb on greased grill over medium-high heat; cover and cook, basting with marinade, for 5-7 minutes on each side for medium-rare or until desired readiness. Season with salt to taste.
Serve with sauted zucchini slices and sweet potatoes.