1In shallow glass bowl or plastic dish, or resealable food-storage plastic bag, mix all ingredients except beef and nectarines.
2Make cuts about 1/2 inch apart and 1/8 inch deep in diamond pattern in both sides of beef. Place beef in marinade in bowl; turn to coat. Cover dish or seal bag; refrigerate, turning occasionally, at least 4 hours but no longer than 24 hours.
3Heat coals or gas grill for direct heat. Remove beef from marinade; reserve marinade.
4Cover and grill beef over medium heat 12 to 14 minutes for medium doneness (160°F), brushing occasionally with marinade and turning once. Add nectarines to grill for last 5 minutes of grilling, turning once and brushing frequently with marinade. Discard any remaining marinade. Cut beef diagonally across grain. Serve with nectarines.