Cook the ramen noodles according to package instructions, drain, and set aside.
In a large skillet or wok, heat the vegetable oil over medium-high heat. Add the sliced chicken and cook until browned and cooked through, about 5-7 minutes.
Add the minced garlic and ginger to the skillet, stirring for about 30 seconds until fragrant.
Add the mixed vegetables to the skillet and stir-fry for another 3-4 minutes until they are tender-crisp.
Pour in the soy sauce, oyster sauce, and sesame oil, stirring to combine.
Add the cooked ramen noodles to the skillet, tossing everything together until the noodles are heated through and well coated with the sauce.
Remove from heat and garnish with sliced green onions and sesame seeds if desired.