Marinate the beef with all the Marinade ingredients, about 15 minutes.
Heat 1 tablespoon of the oil in a wok or skillet over high heat.
Stir-fry the beef until the beef is browned on the outside but still pink inside. Dish out and set aside.
Heat the remaining oil in a wok or skillet over high heat. Stir-fry the garlic and the ginger until aromatic, and then add the green bell pepper, red bell pepper, onion, and black pepper. Stir-fry until you smell the aroma from the ingredients in the wok.
Transfer the beef back into the wok or skillet. Stir-fry until the beef is cooked through and the center of the meat is no longer pink, about 1-2 minutes. Dish out and serve immediately with steamed rice.