In a bowl, combine the sliced beef with the marinade ingredients: soy sauce, oyster sauce, cornstarch, sesame oil, and black pepper. Mix well and let it marinate for about 20-30 minutes.
Heat 1 tablespoon of vegetable oil in a wok or a large skillet over high heat. Add the marinated beef and stir-fry until it’s browned and cooked to your desired level of doneness. Remove the beef from the wok and set it aside.
In the same wok, add another tablespoon of vegetable oil. Add the sliced onions and stir-fry for a couple of minutes until they start to soften.
Add the sliced bell peppers and continue to stir-fry for another 2-3 minutes until they are slightly tender.

Push the vegetables to the sides of the wok, creating a space in the center. Add the minced garlic and ginger to the center and stir-fry for about 30 seconds until fragrant.
Mix the garlic and ginger with the vegetables, then return the cooked beef to the wok.
Add black pepper, soy sauce, oyster sauce, and sugar to the wok. Stir-fry everything together for another 2 minutes, allowing the flavors to meld.
Pour in the beef broth or water to create a sauce. Bring it to a simmer and let it cook for a couple of minutes until the sauce thickens slightly.
Taste and adjust the seasoning if needed. If you prefer more heat, you can add a pinch of red pepper flakes or additional black pepper.
Once the sauce has thickened, remove the wok from the heat. Garnish the Pepper Steak with chopped green onions.
Serve the Chinese Pepper Steak with Onions over steamed rice or noodles.
Enjoy your homemade Chinese Pepper Steak with Onions! Feel free to customize the recipe by adding other vegetables like mushrooms, carrots, or snow peas, according to your taste preferences.