Cut the sirloin steak, bell peppers, red onions, and zucchini into evenly sized pieces.
Add the steak to a bowl or bag with the marinade. Cover and refrigerate for at least 30 minutes, or up to 8 hours.
If using wooden skewers, soak them in water for 20-30 minutes before grilling.
Thread the steak, bell peppers, red onions, zucchini, and cherry tomatoes onto skewers, alternating the ingredients.
Preheat the grill to medium-high heat.
Place the kebabs on the grill and cook for 8-10 minutes, turning occasionally, until the steak is cooked to your preferred doneness and the vegetables are tender.
Remove from the grill and let the kebabs rest for a few minutes before serving.