In a medium bowl, combine soy sauce, oyster sauce, and cornstarch. Thinly slice your beef steak against the grain for maximum tenderness, then add it to the marinade. Toss well to coat and let it marinate for at least 15 minutes.

While the beef marinates, wash and slice your bell peppers into strips. Peel and thinly slice the onion, then mince the garlic and grate the ginger.

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

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

Add minced garlic and grated ginger to the skillet, stirring for about 1 minute until fragrant, then return the cooked beef to the skillet. Pour in beef broth or water and mix well.

Taste and adjust seasoning with salt and pepper. Serve the Pepper Steak with Bell Peppers and Onion hot over rice or noodles.