In a mixing bowl, combine soy sauce, oyster sauce, and cornstarch to create a marinade. Add thinly sliced beef steak, ensuring every piece is coated well. Let it marinate for at least 15 minutes.

Heat 1 tablespoon of vegetable oil in a large skillet over high heat. Add the marinated beef in a single layer, searing for 1-2 minutes on each side until browned. Transfer the beef to a plate and keep warm.

In the same skillet, add another tablespoon of vegetable oil and reduce heat to medium-high. Add sliced bell peppers and onions, sautéing for 3-4 minutes until they are tender yet still slightly crunchy.

Introduce minced garlic and grated ginger to the skillet with the sautéed vegetables. Sauté for about 1 minute until fragrant, being careful not to burn the garlic.

Return the seared beef to the skillet and pour in the beef broth. Stir everything together and allow to simmer for 2-3 minutes, helping the flavors meld while the sauce thickens.

Adjust the seasoning with salt and pepper according to your preference. Serve hot over a bed of steamed rice or noodles.