Most grocers can supply a frozen goose at any time; during the holidays fresh birds are usually available.
Roast the bird in the oven as you would any other large fowl, but prick its skin occasionally to let out excess grease. A 9-pound bird (which feeds 6 to 8 people), put into the oven unstuffed and at room temperature, will take about 2 hours to cook at 325 degrees F. A 12-1/2 pound goose (which feeds 12-14 people) takes 2 hours and 30 to 40 minutes. Add 20 to 40 minutes if the bird is stuffed. Your goose is cooked when its juices run pale yellow; the breast meat will dry out of the goose is cooked too long.