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

While the beef is marinating, slice your vibrant bell peppers and onion into thin strips. Mince the garlic and grate the ginger.

Heat 1 tablespoon of vegetable oil in a large skillet over high heat until shimmering. Add the marinated beef in a single layer, searing for about 1-2 minutes per side until nicely browned.

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

Add the minced garlic and grated ginger to the skillet, sautéing for an additional minute until fragrant.

Return the seared beef to the skillet with the sautéed vegetables. Pour in about 1/2 cup of beef broth or water and let it simmer on medium heat for 2-3 minutes.

Taste and adjust the seasoning with salt and pepper as desired. Serve hot over rice or noodles.