01 - Whisk together olive oil, soy sauce, lemon juice, minced garlic, dried oregano, black pepper, and salt in a medium bowl until fully combined.
02 - Add beef cubes to the marinade, toss thoroughly to coat, cover, and refrigerate for at least 1 hour or up to 8 hours for enhanced flavor.
03 - If using wooden skewers, soak them in water for 30 minutes before grilling to prevent burning during cooking.
04 - Preheat grill or grill pan to medium-high heat, approximately 375-400°F, ensuring even cooking surface temperature.
05 - Thread marinated beef cubes, bell pepper pieces, and red onion wedges alternately onto skewers, leaving small space between pieces for even heat circulation.
06 - Brush assembled kebabs lightly with 2 tablespoons olive oil and season generously with salt and pepper on all sides.
07 - Grill kebabs for 10-12 minutes, turning every 3-4 minutes, until beef reaches desired doneness (130-135°F for medium-rare, 140-145°F for medium) and vegetables show light charring.
08 - Remove kebabs from grill and let rest for 2-3 minutes on a clean plate to allow juices to redistribute, then serve immediately.