Preheat the oven to 400 degrees F (200 degrees C). Place potatoes on a baking sheet; rub with canola oil.
Bake in the preheated oven until easily pierced with a knife, about 1 hour. Reduce oven temperature to 350 degrees F (175 degrees C).
Cut potatoes in half lengthwise. Scrape flesh into the bowl of a stand mixer, being careful not to tear the skin. Leave a small rim of flesh in the skin intact. Place hollowed-out potato skins back on the baking sheet.
Beat butter, gravy, cream cheese, salt, and pepper into the potato flesh on low speed. Add 1 cup Cheddar cheese; mix for a few seconds. Remove bowl from the stand mixer; fold in turkey, stuffing, and green onions using a spatula.
Fill potato skins with the mixture. Sprinkle remaining 1/4 cup Cheddar cheese on top.
Return to the oven; bake until warmed through, about 15 minutes.