Begin by preparing all ingredients before cooking - slice the chicken and vegetables, mince the garlic and ginger, and measure out the sauces.
Heat the vegetable oil in a large skillet or wok over medium-high heat.
Once hot, add the sliced chicken to the skillet. Stir-fry for about 5 minutes or until the chicken is cooked through and no longer pink.
Add the minced garlic and ginger to the skillet and stir-fry for an additional 30 seconds until fragrant.
Add the bell pepper, broccoli, and snap peas to the skillet, and stir-fry for about 2-3 minutes, or until the vegetables are tender-crisp.
Pour in the soy sauce and oyster sauce, stirring to combine. Cook for another minute.
If you prefer a thicker sauce, stir in the cornstarch mixture and cook for an additional minute, allowing it to thicken.
Remove from heat and garnish with chopped green onions.
Serve immediately over cooked rice or noodles if desired.