01 - In a large bowl, whisk together olive oil, soy sauce, lemon juice, minced garlic, dried oregano, black pepper, and salt until well combined.
02 - Add beef cubes to the marinade and toss to coat thoroughly. Cover the bowl and refrigerate for at least 1 hour, or up to 8 hours for deeper flavor penetration.
03 - Preheat grill to medium-high heat, approximately 400°F.
04 - In a separate bowl, toss bell pepper and onion pieces with 1 tablespoon olive oil, 1/2 teaspoon salt, and 1/2 teaspoon black pepper until evenly coated.
05 - Thread beef, peppers, and onions alternately onto skewers, beginning and ending with a piece of beef for secure placement and even cooking.
06 - Place skewers on the preheated grill and cook for 10 to 12 minutes, turning occasionally, until beef reaches desired doneness and vegetables are charred and tender.
07 - Remove kebabs from grill and let rest for 5 minutes before serving to allow juices to redistribute throughout the meat.