01 - In a large bowl, whisk together the olive oil, soy sauce, Worcestershire sauce, lemon juice, minced garlic, dried oregano, smoked paprika, black pepper, and salt until well combined.
02 - Add the sirloin cubes to the marinade and toss to coat evenly. Cover the bowl and refrigerate for at least 1 hour, or up to 8 hours for deeper flavor penetration.
03 - Preheat your grill to medium-high heat, approximately 400°F. If using wooden skewers, soak them in water for at least 30 minutes to prevent burning.
04 - Thread the marinated steak cubes, bell peppers, red onion, zucchini, and mushrooms onto the skewers, alternating ingredients to create colorful, even distribution.
05 - Place the kabobs on the preheated grill and cook for 10 to 12 minutes, turning every 3 to 4 minutes, until the steak is browned and reaches your desired doneness and the vegetables are tender-crisp.
06 - Remove the kabobs from the grill and let them rest for 5 minutes. Garnish with fresh chopped parsley and serve with lemon wedges if desired.