01 - In a medium bowl, combine the olive oil, soy sauce, lemon juice, Worcestershire sauce, minced garlic, brown sugar, dried oregano, and black pepper. Whisk until the sugar dissolves and the mixture is well blended.
02 - Place the sirloin cubes in a large resealable plastic bag or shallow dish. Pour the marinade over the steak, seal or cover tightly, and refrigerate for 1 to 2 hours. For deeper flavor, marinate overnight.
03 - Preheat your outdoor grill or grill pan to medium-high heat, approximately 400°F. If using wooden skewers, soak them in water for at least 30 minutes beforehand to prevent burning.
04 - Thread the marinated steak cubes and prepared vegetables onto the skewers, alternating colors and ingredients for an appealing presentation. Distribute the pieces evenly across all skewers.
05 - Place the skewers on the preheated grill. Cook for 10 to 15 minutes, turning every 2 to 3 minutes with tongs, until the steak reaches your desired doneness and the vegetables are lightly charred with tender-crisp texture.
06 - Remove the kabobs from the grill and let them rest for 5 minutes to allow the juices to redistribute. Serve immediately while hot.