Skewer onto remaining 8 vine skewers alternating with mushrooms.
In small bowl, combine 2 tablespoons olive oil and balsamic vinegar. Brush vegetables with this mixture and season to taste.
Grill beef skewers for 2 to 3 minutes per side (8 to 10 minutes total cooking time for medium-rare doneness), basting frequently with remaining marinade.
When beef has been cooking 3 minutes, place vegetable skewers on grill and cook for 6 to 8 minutes until tender, brushing with remaining oil and vinegar mixture.