In a bowl, combine the marinade ingredients: soy sauce, fish sauce, worcestershire sauce, rice wine, sugar, and black pepper. Combine with the sliced flank steak and let it marinade for an hour at room temperature.
In a small bowl, combine the soy sauce, rice wine, red pepper flakes, and cornstarch for the sauce.
Heat a wok over high heat. Add the peanut oil and sear ½ of marinaded flank steak until it has browned. Remove, add additional oil if needed, and repeat with the remaining half of the flank steak.
Remove the steak and wipe down the wok. Add the garlic, ginger, and scallions and cook for 30 seconds to soften. Add half of the cut peppers and onions and cook until softened. Remove, add additional oil if needed, and repeat with the remaining peppers and onions.
Once the last half of the peppers and onions have softened return the steak, pepper, and onions to the wok.
Toss together and add the sauce. Cook until the sauce has slightly thickened. Serve in a bowl over cooked rice.
