Combine the Worcestershire sauce, soy sauce, olive oil, Dijon mustard, garlic, brown sugar, lemon juice, basil, parsley, and black pepper in a mixing bowl. Whisk until smooth and well blended. The combination of these ingredients creates a savory, tangy, and slightly sweet marinade that enhances the steak’s natural flavor.
Place the cubed steak in a large plastic bag or shallow dish. Pour the marinade over the steak, ensuring each piece is fully coated. Seal the bag (or cover the dish) and refrigerate for a minimum of 1 hour, though marinating for up to 24 hours will develop deeper flavor. If using wooden skewers, soak them in water at this time to prevent burning on the grill.
Boil the potatoes in salted water until they’re fork-tender, about 6–8 minutes. Drain and toss them in olive oil, rosemary, and mustard for seasoning. Chop your other vegetables into evenly sized pieces to ensure they cook uniformly. Brush them lightly with leftover marinade for added flavor.
Thread the marinated steak onto skewers, alternating with vegetables like potatoes, mushrooms, peppers, and onions. Aim for about 4–5 pieces of steak per skewer for balanced servings.
Preheat your grill to high heat, then reduce it slightly to medium-high. Place the kabobs directly on the grill grates and cook for 8–10 minutes, turning every 2–3 minutes. Look for a nice char on the edges without overcooking the steak. Medium-rare to medium is ideal for juicy steak kabobs.
Once the kabobs are done, allow them to rest for 5 minutes off the grill. This helps the juices redistribute, making the meat more flavorful and tender. Serve immediately.