In a small bowl combine oregano, cracked pepper, lemon peel, and 2 cloves of the garlic. Use your fingers to rub the mixture onto all sides of the meat.
In a grill with a cover, arrange hot coals around a drip pan. Test for medium-hot heat above the pan. Place meat on grill rack over drip pan. Brush eggplants, sweet peppers, and onion slices with olive oil. Arrange vegetables on edges of grill rack directly over coals. Cover and grill for 10 to 12 minutes or until vegetables are tender, turning once. Remove vegetables from grill; set aside. Cover grill and continue grilling meat for 25 to 30 minutes more or until a meat thermometer inserted in the center registers 135 degrees for medium-rare doneness. Cover; let stand for 15 minutes before slicing.
Meanwhile, for relish, coarsely chop grilled vegetables. In a medium bowl combine grilled vegetables, tomatoes, olives, basil, the remaining garlic clove, the vinegar, salt, and the ground black pepper. Serve the beef with relish. Makes 10 servings.