Begin by cooking the rice noodles according to the package instructions. Drain and set aside.
In a large frying pan or wok, heat the vegetable oil over medium-high heat.
Add the thinly sliced beef sirloin to the pan. Stir-fry for about 5-7 minutes, or until the beef is browned and cooked through. Remove from the pan and set aside.
In the same pan, add minced garlic and grated ginger. Sauté for about 30 seconds until fragrant.
Add the sliced bell pepper and broccoli florets to the pan. Stir-fry for approximately 3-5 minutes, or until the vegetables are tender but still crisp.
In a bowl, mix together the soy sauce, oyster sauce, hoisin sauce, brown sugar, and sesame oil. Pour this sauce into the pan with the vegetables.
Return the cooked beef to the pan and stir everything together until well combined. Cook for an additional 2-3 minutes to heat through.
Add the cooked rice noodles to the pan, tossing gently to coat them with the sauce and mix well with the beef and veggies.
Season with salt and pepper to taste.
Serve hot, garnished with sesame seeds and chopped green onions.