Make marinade by whisking all the ingredients into a bowl.
Pour half of this over the steaks and let marinade in the refrigerator for at least 1 hour.
Cut up the cauliflower, red peppers, button mushrooms and zucchini into chunks and layer them onto bamboo skewers and transfer to a casserole dish where they can lay flat. Pour the remaining marinade over the vegetable skewers.
Heat the grill until it is very hot. Add the steaks and grill until medium rare, turning once, about 8 - 14 minutes depending on the heat of the grill. Add the skewers and grill just until the vegetables are soft and charred, a few minutes at most.
Serve the steaks with the vegetable skewers on the side. Serve with rice or couscous.