Lightly grease a baking pan with cooking spray. Set aside.
In a non-stick wok, heat oil over medium heat and cook the sausage and onions for about 4-6 minutes.
Add in the sliced mushrooms and cook for about 6-7 minutes.
Remove from oven and drain the grease from the wok.
In a bowl, add sausage mixture, beaten eggs, garlic salt, cheese and Alfredo sauce and stir to combine.
Place the sausage mixture into the prepared baking dish.
Slide the Air Fryer Basket inside and adjust the temperature of Air Fryer to 390 °F to preheat for 5 minutes.
After preheating, arrange the baking dish into the Air Fryer Basket.
Slide the basket into Air Fryer and set the time for 12 minutes.
After cooking time is finished, remove the baking dish from Air Fryer and place onto a cooling rack to cool for about 5 minutes before serving.
Cut the casserole into equal-sized wedges and serve with the topping of remaining cheese.