In a bowl, combine the sliced beef with soy sauce, oyster sauce, hoisin sauce, cornstarch, and sesame oil. Let it marinate for at least 15-20 minutes.
Heat 1 tablespoon of vegetable oil in a wok or a large skillet over medium-high heat. Add the marinated beef to the hot wok and stir-fry until browned and cooked through. Remove the beef from the wok and set it aside.
In the same wok, add another tablespoon of vegetable oil. Add minced garlic and ginger, and stir-fry for about 30 seconds until fragrant.
Add sliced onions, bell peppers, julienned carrots, broccoli florets, and snap peas to the wok. Stir-fry for 3-4 minutes until the vegetables are tender-crisp. Return the cooked beef to the wok with the vegetables.
Pour in 1/4 cup of water to create a sauce and stir everything together. Cook for an additional 2-3 minutes until the beef and vegetables are well-coated and heated through.
Adjust seasoning if necessary. You can add a bit more soy sauce or salt if desired. Serve the Chinese Beef with Vegetables over cooked white rice. Garnish with chopped green onions or sesame seeds if you like.