In a large saucepan, heat the oil over medium heat. Add in the onion and cook until the onions are translucent and fragrant.
Mix in the garlic powder and chicken broth and bring to a boil. Reduce heat and simmer for around 10 minutes.
Mix in the frozen mixed vegetables and simmer for around 5 minutes.
In a medium bowl, whisk together the flour and milk until smooth.
Slowly mix the milk mixture into the soup. Add in the salt, pepper and cayenne pepper, stiring until thickened, around 15 minutes.
Mix in the turkey and cheese until the cheese is melted. Enjoy warm.