01 - In a large bowl, whisk together olive oil, soy sauce, lemon juice, minced garlic, dried oregano, black pepper, and salt. Add beef cubes and toss to coat thoroughly. Cover the bowl and refrigerate for at least 1 hour, up to 8 hours for deeper flavor penetration.
02 - Preheat grill to medium-high heat, approximately 400°F. Ensure grates are clean and lightly oiled to prevent sticking.
03 - In a separate bowl, combine bell pepper and red onion pieces with 1 tablespoon olive oil, 1/2 teaspoon salt, and 1/2 teaspoon black pepper. Toss until vegetables are evenly coated.
04 - Thread beef cubes, bell peppers, and onion pieces alternately onto skewers, beginning and ending with a piece of beef for even cooking. Leave slight space between pieces to allow heat circulation.
05 - Place kebabs on the preheated grill. Cook for 10 to 12 minutes, turning occasionally to ensure even charring on all sides. Grill until beef reaches desired doneness and vegetables are tender-crisp with light char marks.
06 - Remove kebabs from grill and let rest for 5 minutes before serving. This allows juices to redistribute throughout the meat for optimal tenderness.