In a small mixing bowl, whisk together soy sauce, rice vinegar, sesame oil, and cornstarch. Add in beef broth, sugar, black pepper, ginger, and garlic. Whisk to combine. Set aside.
Heat 2 tablespoons of vegetable oil in a wok over high heat. Add in beef and toss until seared, about 2-3 minutes. Remove from wok and set aside.
Add in another 2 tablespoons of vegetable oil. Add in peppers and onions. Cook in the wok until tender crisp, about 3 minutes.
Add meat back into the wok. Add in ginger garlic sauce. Stir and cook about 1 minute.
Garnish with sliced green onions (optional) and serve hot.