Steps
1. In a small bowl, whisk together soy sauce, oyster sauce, black pepper, cornstarch, and water. Set aside.
2. Heat vegetable oil in a pan over medium-high heat. Add sliced beef and cook until browned. Remove from pan and set aside.
3. In the same pan, add bell pepper, onion, and garlic. Stir fry for 2-3 minutes until vegetables are slightly tender.
4. Return the beef to the pan and pour the sauce mixture over it. Stir well to coat everything evenly.
5. Cook for an additional 2 minutes until the sauce thickens and coats the beef and vegetables.
6. Serve hot with steamed rice or noodles.