In a medium bowl, combine the thinly sliced beef with 2 tablespoons of soy sauce, 1 tablespoon of cornstarch, and 1 teaspoon of sesame oil.

Toss the beef to ensure it is evenly coated, then set it aside to marinate for at least 15 minutes.

You can marinate it longer in the refrigerator if you have more time.

Wash and prepare all the vegetables by cutting them into uniform, bite-sized pieces for even cooking.

This includes broccoli florets, julienned carrots, sliced bell peppers, snow peas, and sliced onion.

In a small bowl, whisk together 1/4 cup of soy sauce, 2 tablespoons of oyster sauce, 1 tablespoon of rice vinegar, and 1 tablespoon of brown sugar.

Stir in the grated ginger and minced garlic until the sauce is well combined and the sugar has dissolved.

Heat 1-2 tablespoons of vegetable oil in a large wok or skillet over high heat until it begins to smoke.

Add the marinated beef in a single layer and cook for 2-3 minutes per side until browned, then remove the beef and set it aside.

Add a little more oil if needed, then add the prepared vegetables to the hot wok, starting with harder vegetables like carrots and broccoli.

Stir-fry the vegetables for 3-5 minutes until they are crisp-tender.

Return the cooked beef to the wok with the vegetables, pour the stir fry sauce over everything, and toss to coat.

Cook for another 1-2 minutes until the sauce slightly thickens.

Serve the beef stir fry immediately over steamed rice or noodles.

Garnish with sesame seeds or sliced green onions if desired.