Slice the Beef. Thinly slice the beef against the grain to ensure tenderness.
Chop the Vegetables. Prepare all the vegetables by slicing them into bite-sized pieces.
Make the Sauce. In a small bowl, whisk together soy sauce, oyster sauce, cornstarch, and chicken broth.
Heat the Wok. Heat a large wok or skillet over high heat and add a bit of oil.
Cook the Beef. Add the sliced beef and stir-fry until browned and cooked through. This should take 3-4 minutes. Remove from the wok and set aside.
Stir-Fry the Aromatics. Add more oil to the wok if needed, then add garlic and ginger, cooking until fragrant.
Add the Vegetables. Toss in the celery, bell peppers, bok choy, bean sprouts, carrots, and mushrooms. Stir-fry until the vegetables are tender-crisp, 8-10 minutes.
Return the Beef. Add the beef back to the wok.
Add the Sauce. Pour the sauce over the beef and vegetables, stirring until everything is well coated and the sauce has thickened.