Add apples, sugar, and butter to a non-stick pan. Cook over low-medium heat, then stir in the cinnamon and vanilla. Allow it to reduce into a syrup consistency until the apples are tender but still somewhat firm.
Add the milk and oats to a saucepan over medium heat and stir until combined. Cook according to the instructions on the package. Season with salt. Once cooked, cover with a lid and set aside.
Heat the oil in a pan over medium heat. Sauté the spinach until wilted and season with salt and pepper. Move to the side of the pan and brown the sausage slices on both sides.
Spoon the apples over the oatmeal, and serve with chicken sausage and spinach.