01 - Whisk together olive oil, soy sauce, lemon juice, minced garlic, dried oregano, black pepper, and salt in a bowl until well combined.
02 - Add beef cubes to the marinade, toss thoroughly to coat, cover the bowl, and refrigerate for at least 1 hour, up to 4 hours for optimal flavor infusion.
03 - If using wooden skewers, soak them in water for at least 30 minutes prior to grilling to prevent burning during cooking.
04 - Thread marinated beef cubes, bell pepper pieces, and onion chunks onto skewers in an alternating pattern, distributing ingredients evenly.
05 - Lightly brush assembled kebabs with olive oil and season with additional salt and pepper to taste.
06 - Preheat grill or grill pan over medium-high heat until hot, approximately 5 minutes.
07 - Place kebabs on the hot grill and cook for 10 to 15 minutes, turning every 3 to 4 minutes, until beef reaches desired doneness and vegetables are slightly charred and tender.
08 - Transfer cooked kebabs to a serving platter and let rest for 5 minutes before serving to allow juices to redistribute.