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, and refrigerate for at least 1 hour, up to 4 hours for optimal flavor absorption.
03 - If using wooden skewers, soak 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 alternately onto skewers, distributing ingredients evenly.
05 - Lightly brush assembled kebabs with olive oil and season with salt and pepper to taste.
06 - Heat grill or grill pan to medium-high temperature, approximately 400°F.
07 - Grill kebabs for 10 to 15 minutes, rotating every few minutes, until beef reaches desired doneness and vegetables are tender with slight charring.
08 - Allow kebabs to rest for 5 minutes before serving to let juices redistribute throughout the meat.