Prepare the slow cooker by lightly coating it with cooking spray.
Brush the turkey wings with olive oil and set them aside.
In a small bowl, combine the garlic powder, onion powder, salt, paprika, and black pepper. Stir until well mixed.
Rub the seasoning mixture over each side of the turkey wings.
Transfer the seasoned turkey wings into the prepared slow cooker.
Pour 1 cup of water into the bottom of the slow cooker.
Cover and cook the turkey wings on low for 6-8 hours or on high for 3-4 hours, until the meat is tender and cooked through.
Optionally, for crispy skin, transfer the cooked turkey wings to a baking sheet and place them under the broiler for a few minutes until the skin is golden brown and crispy.
Serve the slow cooker turkey wings on a serving platter, garnished with fresh parsley if desired.