In a small bowl, whisk together orange juice, soy sauce, oyster sauce, vinegar, chilli sauce and cornflour; set aside.
Heat 1 teaspoon of the oil in a large non-stick wok or frying pan over high heat. Add half of the steak and cook, without stirring or turning, until browned on the underside, about 1 minute. Stir and turn the slices, then cook just until browned on the other side, about 30 seconds. Transfer to a plate. Add another 1 teaspoon oil, repeat with the remaining steak and transfer to the plate.
Add remaining oil to the frying pan, then add ginger, orange zest and garlic and stir-fry until fragrant, 10 to 20 seconds. Add onion and stir-fry for 1 minute. Add the broccoli and capsicum and stir-fry for 30 seconds. Add ¼ cup water, cover, and cook just until crisp-tender, about 1½ minutes. Push vegetables to the outside of the pan. Stir the reserved sauce, pour into the centre of the pan and cook, stirring, until glossy and thickened, about 1 minute. Stir vegetables into the sauce, return steak to the wok and turn to coat. Serve with rice.