01 - Combine sliced flank steak with soy sauce, Shaoxing wine, cornstarch, and black pepper in a bowl. Mix thoroughly to coat all pieces. Allow to marinate for 10 to 15 minutes at room temperature.
02 - Whisk together soy sauce, oyster sauce, hoisin sauce, sugar, beef broth, and cornstarch in a small bowl until cornstarch is fully dissolved. Set aside until ready to use.
03 - Heat 1 tablespoon vegetable oil in a large wok or skillet over high heat until smoking. Add marinated beef in a single layer without overcrowding. Sear for 1 to 2 minutes until browned but still slightly pink inside. Remove beef from pan and set aside on a plate.
04 - Add remaining tablespoon of oil to the wok. Add onion wedges, bell pepper strips, garlic, and ginger. Stir-fry over high heat for 2 to 3 minutes until vegetables are crisp-tender and fragrant.
05 - Return seared beef to the wok with vegetables. Pour in prepared sauce and toss everything together. Continue stir-frying for 1 to 2 minutes until sauce thickens and coats all ingredients evenly. Season with additional black pepper to taste.
06 - Transfer pepper steak to a serving platter or divide among plates. Serve immediately while hot with steamed white rice.