01 - In a large mixing bowl, whisk together olive oil, soy sauce, lemon juice, minced garlic, dried oregano, black pepper, and salt.
02 - Add beef cubes to the marinade, toss to coat evenly, cover, and refrigerate for at least 1 hour, or overnight for enhanced flavor.
03 - Heat the grill to medium-high, approximately 400°F (200°C).
04 - Thread beef, bell peppers, and red onion alternately onto skewers, leaving small gaps between pieces for even cooking.
05 - Cook the skewers for 10 to 12 minutes, turning every 2 to 3 minutes, until the beef reaches desired doneness and vegetables are tender with slight charring.
06 - Remove kebabs from grill and let rest for 5 minutes before serving hot.