Combine olive oil, balsamic vinegar, worcestershire and steak spice. Marinate beef chunks for at least 4 hours or over night.
If using wooden skewers, soak in tall glass of water for 2-4 hours, flipping if necessary.
Cut vegetables into chunks. Bring pot of water to boil. Add all veggies except tomatoes to boiling water for 1 minute. Drain and immediately add to large bowl of ice water.
Thread meat and vegetables onto skewers in alternating pattern, with onion beside each chunk of meat. Top with cherry tomato or mushroom. Use 5 chunks of beef and each vegetable once on each skewer for best presentation.
Grill on high, turning frequently until meat and veggies are well charred and meat is medium rare.