Cook the noodles according to the package instructions. Drain and set aside.
Heat the vegetable oil in a wok or large skillet over medium-high heat.
Add the sliced chicken to the pan. Season with salt and pepper, and stir-fry for about 5-7 minutes or until fully cooked. Remove from the pan and set aside.
In the same pan, add the garlic and ginger. Cook for 30 seconds until fragrant.
Add the sliced bell pepper, broccoli, and snap peas. Stir-fry for about 3-4 minutes until the vegetables are tender-crisp.
Return the cooked chicken to the pan, and add the cooked noodles, soy sauce, oyster sauce (if using), and sesame oil. Toss everything together until well combined and heated through, about 2-3 minutes.
Taste and adjust seasoning as necessary. Serve hot, garnished with chopped green onions.