In a small bowl, mix cornstarch and water until smooth and set aside.
Heat vegetable oil in a large pan or wok over medium-high heat.
Add ground turkey, season with salt and pepper, and cook until browned and cooked through, about 5-7 minutes. Remove from pan and set aside.
In the same pan, add garlic and ginger; sauté for 30 seconds until fragrant.
Add bell pepper, broccoli, carrot, and snap peas; stir-fry for 4-5 minutes until vegetables are tender-crisp.
Return the turkey to the pan and stir to combine with the vegetables.
Pour in soy sauce, oyster sauce, sesame oil, crushed red pepper flakes, and the cornstarch mixture.
Cook, stirring constantly, until sauce thickens and coats the meat and vegetables, about 2 minutes.
Remove from heat and garnish with sliced green onions.
Serve immediately over cooked white rice.