Heat grill. Cut into side of each steak, forming a deep pocket; do not cut through to the other side. Mix pesto and cheese and spoon into pockets. Press closed and drizzle oil over beef. Place steaks carefully on grill and cook 5 inches from medium coals for 12-15 minutes for medium doneness, turning once. Remove from grill, cover and let stand for 5-10 minutes. Cut beef into thick strips to serve.