Begin by cooking the egg noodles according to the package instructions. Once cooked, drain them in a colander and set aside.
In a large skillet or wok, heat the vegetable oil over medium-high heat.
Add the diced onion and sauté for about 2-3 minutes until it becomes translucent.
Stir in the minced garlic, cooking for another 30 seconds until fragrant.
Add the ground beef to the skillet, breaking it up with a spoon or spatula. Cook for about 5-7 minutes until the beef is browned and no longer pink.
Add the sliced bell pepper and snap peas (or green beans) to the skillet, stirring well. Cook for an additional 3-4 minutes until the vegetables are just tender.
In a small bowl, combine the soy sauce, hoisin sauce, oyster sauce, ground ginger, salt, and pepper. Pour the sauce over the beef and vegetable mixture, stirring to combine.
Add the cooked noodles to the skillet and gently toss everything together until the noodles are well coated in the sauce and heated through (about 2-3 minutes).
Remove from heat and garnish with chopped green onions before serving.
If desired, add red pepper flakes or Sriracha to the sauce for a spicier version.