In a medium bowl, mix together soy sauce, oyster sauce, and cornstarch until smooth. Add the thinly sliced beef and toss to coat evenly. Let the beef marinate for at least 15 minutes.

While the beef is marinating, slice the bell peppers and onion into thin strips for even cooking. Mince the garlic and grate the ginger finely.

Heat a large skillet or wok over medium-high heat and add vegetable oil. Once hot, add the marinated beef in a single layer, searing for 1-2 minutes on each side until browned.

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

Stir in the minced garlic and grated ginger to the skillet. Cook for an additional minute until fragrant.

Return the seared beef to the skillet, pouring in the beef broth or water. Stir everything together and cook for another 2-3 minutes to thicken the sauce.

Season your pepper steak with salt and pepper to taste, stirring well. Serve hot over freshly steamed rice or noodles.