Cook the rice noodles according to package instructions. Drain and set aside.
In a small bowl, mix together soy sauce, hoisin sauce, oyster sauce, brown sugar, and sesame oil. Set aside.
Heat vegetable oil in a large skillet or wok over medium-high heat. Add the sliced flank steak and cook for 3-4 minutes until browned. Remove the beef and set aside.
In the same skillet, add garlic and ginger, sautéing for about 30 seconds until fragrant.
Add the red bell pepper and snap peas to the skillet, cooking for 2-3 minutes until slightly tender.
Return the beef to the skillet, then pour the sauce mixture over the beef and vegetables. Stir to coat everything evenly.
Add the cooked rice noodles to the skillet, tossing gently to combine all ingredients. Cook for an additional 2-3 minutes until heated through.
Serve immediately, garnished with chopped green onions and sesame seeds if desired.