In a large container, whisk together the lemon juice, oil, garlic, oregano or mint, salt, and pepper.
Trim the lamb (or beef) and cut into 1 1/2″ cubes. Add to the marinade. Cover and refrigerate for 8 hours or overnight. Stir occasionally to coat the lamb (or beef).
Core, seed, and cut the green peppers into 1 1/4″ cubes.
Cut the zucchini into 1″ pieces.
Thread the lamb (or beef), bell peppers, zucchini, onions, and bay leaves onto 8 metal skewers. Alternate the ingredients as evenly as possible.
Place on a heated grill and cook for 25 – 30 minutes, turning every 5 minutes for even cooking.
Serve hot, garnished with lemon wedges, with a bowl of Tzatziki.
Alternate Grilling Method:
Place skewered kabobs on a greased broiler pan. Place under broiler, and cook for 10 – 15 minutes, turning frequently until cooked.