Steps
1. In a bowl, combine soy sauce, oyster sauce, cornstarch, black pepper, and minced garlic. Add the sliced beef and toss to coat. Let it marinate for 10 minutes.
2. Heat vegetable oil in a wok or a large skillet over high heat. Add the marinated beef and stir-fry for 2-3 minutes until browned. Remove the beef from the wok and set aside.
3. In the same wok, add the sliced bell peppers and onion. Stir-fry for 2-3 minutes until they are slightly tender.
4. Return the cooked beef to the wok and stir-fry for an additional minute to combine the flavors. Drizzle with sesame oil and toss to coat.
5. Serve the peppered garlic beef stir-fry hot, garnished with chopped spring onions. Enjoy!