Begin by marinating the chicken. In a bowl, combine the sliced chicken, soy sauce, and cornstarch. Mix well and let it sit for about 10 minutes while you prepare the vegetables.
Heat a large skillet or wok over medium-high heat. Add 1 tablespoon of vegetable oil and heat until it starts to shimmer.
Add the marinated chicken to the skillet in a single layer. Sauté for about 5-6 minutes or until the chicken is fully cooked and no longer pink. Remove the chicken from the skillet and set aside.
In the same skillet, add the remaining tablespoon of vegetable oil. Add the minced garlic and ginger, stirring for about 30 seconds until fragrant.
Add the sliced bell pepper, broccoli florets, and sliced carrots to the skillet. Stir-fry the vegetables for about 3-4 minutes or until they are tender-crisp.
Return the cooked chicken to the skillet. If desired, add the oyster sauce, and season with salt and pepper to taste. Toss everything together and stir-fry for an additional minute to heat through.
Serve the chicken stir fry hot over cooked rice or noodles.