This quick and easy stir-fry is perfect for a busy weeknight. Start by marinating thinly sliced beef in soy sauce, garlic, and ginger. Then, stir-fry the beef in a hot wok until browned. Remove the beef from the wok and stir-fry broccoli florets until tender-crisp. Add the beef back to the wok and toss with a sauce made from soy sauce, oyster sauce, and cornstarch. Serve over rice.