Cook the yakisoba noodles according to package instructions. Drain and set aside.
Heat vegetable oil in a large pan or wok over medium-high heat. Add the sliced pork or chicken and cook until browned.
Add the sliced onion, julienned carrot, and thinly sliced cabbage to the pan. Stir-fry until vegetables are tender.
Add the cooked yakisoba noodles to the pan along with yakisoba sauce, oyster sauce, and soy sauce. Stir well to combine.
Season with salt and pepper to taste. Cook for another 2-3 minutes until everything is heated through.
Serve hot, garnished with optional toppings if desired.