Prepare and slice the beef and broccoli, ensuring they are ready for cooking.
Mix soy sauce, oyster sauce, minced garlic, grated ginger, and sesame oil to create a marinade. Allow the beef to marinate in this mixture for a minimum of 15 minutes.
Heat a tablespoon of oil in a wok and add broccoli. Stir-fry until broccoli is tender-crisp and bright green. Set aside.
In the same wok, stir-fry marinated beef in batches till browned, making sure not to crowd the pan.
Reintroduce the broccoli to the wok, add some marinade, and combine until everything is well-coated and heated through.
Notes
Store any leftovers in an airtight container and refrigerate for up to 3 days. For a quick reheat, use a microwave or gently warm in a pan.