All you need:

Beef, Red & green capsicum, Onion, Satay sauce, Light soy sauce, Dark soy sauce, Oyster sauce, Potato starch, Ginger

Step1. Marinade beef for 1 hour, cut beef into small pieces and marinade it with 2 spoon of satay sauce, 1 spoon of light soy sauce, 1 spoon of oyster sauce, 1/2 spoon of dark soy sauce, 1 spoon of potato starch, a few drops of cooking oil...