In a bowl, combine the beef strips, soy sauce, and cornstarch. Mix well and set aside for 10 minutes.
Heat the vegetable oil in a large skillet or wok over medium-high heat. Add the sliced onion, bell peppers, garlic, and ginger. Stir-fry for 5 minutes until the vegetables are tender-crisp.
Push the vegetables to one side of the skillet and add the marinated beef. Cook for 3-4 minutes until browned on all sides.
In a small bowl, whisk together the beef broth, oyster sauce, hoisin sauce, and brown sugar. Pour the sauce over the beef and vegetables and simmer for 2-3 minutes until the sauce has thickened.
Serve the pepper steak over rice or noodles. Enjoy!