Marinate beef in 1 tbsp soy sauce, wine and black pepper for 15 minutes.
Make the sauce by mixing oyster sauce, vinegar, ketchup, sugar, sambal, 2 tbsp soy sauce, sesame oil.
Coat beef slices with corn starch and deep fry for 5 minutes or until cooked. Set aside.
In wok with some oil, fry onions, garlic, bell peppers for 2 minutes.
Add sauce into wok and mix well. Let it simmer for 1 minute.
Remove wok from heat and add beef. Toss it to mix well.