Preheat your oven to 400°F (200°C). Remove the goose from the fridge an hour before cooking to bring it to room temperature. Pat the skin completely dry with paper towels.
To make the stuffing, heat the olive oil and butter in a large pan over medium heat. Add the onions and cook for 10 minutes until soft and golden.
Stir in the chopped sage and cook for another minute. Remove from heat and mix in the breadcrumbs, lemon zest, and beaten eggs. Season generously with salt and pepper.
Prick the goose skin all over with a fork (this helps the fat render). Stuff the cavity loosely with the apple and orange quarters to add moisture and flavor.
Shape the sage and onion stuffing into balls and place around the goose in the roasting tin (not inside the bird). Rub the goose skin with salt and pepper.
Roast for 30 minutes, then reduce the heat to 350°F (180°C). Continue roasting for about 2½ hours, draining off the excess fat every 45 minutes (save this gorgeous goose fat for roast potatoes!).
The goose is done when the juices run clear and the internal temperature reaches 165°F. Remove from the oven and let it rest for 30 minutes before carving. Serve with the crispy stuffing balls and all your favorite trimmings!