Preheat oven to 325°. Discard any soft or decayed cranberries.
Mix cranberries, sugar, brandy to taste, and orange zest in an 8- or 9-in. square baking dish. Bake, uncovered, until most of the liquid has evaporated, 1 to 1 1/4 hours, stirring occasionally.
Make ahead: Cover and chill up to 1 week.
Note: Nutritional analysis is per 3-tbsp. serving.