01 - In a large bowl, whisk together soy sauce, olive oil, balsamic vinegar, Worcestershire sauce, minced garlic, brown sugar, smoked paprika, black pepper, and dried thyme until well combined.
02 - Add the steak cubes to the bowl and toss to coat thoroughly with the marinade. Cover and refrigerate for at least 2 hours, up to 8 hours for maximum flavor absorption.
03 - Preheat your grill to medium-high heat, approximately 400-450°F, ensuring the grates are clean and lightly oiled to prevent sticking.
04 - Thread the marinated steak, bell peppers, onion wedges, and mushrooms onto the skewers in an alternating pattern, distributing ingredients evenly among all 8 skewers.
05 - Place kebabs on the preheated grill and cook for 10-15 minutes, turning every 3-4 minutes, until steak reaches desired doneness (130-135°F for medium-rare) and vegetables are lightly charred and tender.
06 - Remove kebabs from the grill and let rest for 5 minutes to allow juices to redistribute. Serve immediately while hot.