In a medium bowl, combine soy sauce, oyster sauce, and cornstarch to create a thick marinade. Add thinly sliced beef steak, tossing well to coat. Allow to marinate for at least 15 minutes.

Slice the bell peppers and onion into thin strips. Finely mince the garlic and grate the ginger.

Heat a large skillet over high heat and add 2 tablespoons of vegetable oil. Once shimmering, add the marinated beef in a single layer. Sear for 1-2 minutes on each side until browned, then set aside.

In the same skillet, add more oil if needed and toss in the bell peppers and onion. Sauté for 3-4 minutes until bright and tender, yet still crisp.

Add the minced garlic and grated ginger to the skillet and sauté for about 1 minute. Return the beef to the pan, pour in beef broth or water, and stir. Cook for another 2-3 minutes until the sauce thickens.

Season with salt and pepper to taste and serve hot over steamed rice or noodles.