In a large skillet or wok, heat the vegetable oil over medium-high heat. Add the diced onion and cook for about 2-3 minutes until softened.
Add the minced garlic and ground turkey to the skillet. Cook, breaking up the turkey with a spatula, until browned and cooked through, about 5-7 minutes.
Stir in the bell pepper, broccoli, snap peas, and carrot. Cook for an additional 3-5 minutes until the vegetables are tender-crisp.
In a small bowl, mix together the soy sauce, oyster sauce (if using), sesame oil, ground ginger, salt, and pepper. Pour this sauce over the turkey and vegetables, stirring to combine. Cook for another 2 minutes to heat through.
Serve the stir-fry over cooked rice or quinoa.