Cook the pancit canton noodles according to package instructions, then drain and set aside.
In a large skillet or wok, heat the vegetable oil over medium heat. Add the sliced onion and minced garlic, sautéing until fragrant and the onion is translucent, about 3 minutes.
Add the julienned carrot, bell pepper, and green beans to the skillet. Stir-fry the vegetables for about 5 minutes, or until they are tender-crisp.
Stir in the shredded chicken, cooked pancit canton noodles, soy sauce, oyster sauce, and sesame oil. Toss everything together until well combined and heated through, about 3-4 minutes.
Season with salt and pepper to taste. Remove from heat and garnish with chopped green onions. Serve with lemon wedges on the side.