Place steak cubes in a large mixing bowl. Pour over beef marinade over, toss, then cover with plastic wrap and refrigerate for 1-3 hours.
After the meat has finished marinating, place the veggies in a separate large bowl and drizzle oil over. Add salt and toss well.
Preheat your grill. Place one piece of steak on a soaked skewer followed by a mushroom, a piece of bell pepper, an onion, a zucchini and another piece of meat. Keep at it until your skewer is filled up. Repeat with remaining kabobs.
Spray your grill with cooking spray. Grill kabobs for about six minutes per side, until meat has cooked through and veggies are tender and a little charred.