In a bowl, whisk together olive oil, soy sauce, Worcestershire sauce, minced garlic, brown sugar, and black pepper.
Place the steak cubes in a zip-top bag or shallow dish. Pour the marinade over the steak and let it sit for at least 30 minutes in the refrigerator for maximum flavor.
Thread the marinated steak cubes onto skewers, alternating with bell peppers, onion, mushrooms, and zucchini slices.
Preheat your grill or grill pan to medium-high heat. Cook the kabobs for 10-15 minutes, turning occasionally, until the steak reaches your desired doneness.
Remove the kabobs from the grill and let rest for 5 minutes. Serve hot with your favorite sides.
