Heat the vegetable oil in a large skillet or wok over medium-high heat.
Add the chicken slices and cook until browned, about 5 minutes. Remove and set aside.
In the same skillet, add garlic and ginger. Sauté for 1 minute until fragrant.
Add the mixed vegetables and stir-fry for 3–4 minutes until tender-crisp.
Return the chicken to the skillet, and add soy sauce, oyster sauce, and sesame oil. Toss everything together to coat evenly.
Cook for an additional 2 minutes to combine the flavors. Season with salt and pepper as needed.
Serve hot over cooked rice or noodles.