In a large skillet or wok, heat the vegetable oil over medium-high heat. Add the ground turkey and cook until browned, about 5-7 minutes, breaking it apart with a spatula as it cooks.
Add the minced garlic and grated ginger to the skillet, stirring for about 1 minute until fragrant.
Toss in the sliced bell peppers, broccoli florets, and snap peas. Stir-fry the vegetables with the turkey for about 5 minutes until they are tender-crisp.
Pour in the teriyaki sauce, soy sauce, and sesame oil. Stir to combine and let it cook for another 2-3 minutes.
If you prefer a thicker sauce, mix the cornstarch with water and add it to the skillet, stirring until the sauce thickens.
Serve the stir fry over cooked rice or quinoa. Garnish with sesame seeds and sliced green onions.