Pour the frozen strawberries into the bowl of a food processor and process until very finely chopped. Remove to a medium sized mixing bowl.
Add the quartered apple to the bowl of the food processor and process until very finely chopped. Scoop into the medium sized mixing bowl with the cranberries.
Add the quartered orange to the bowl of the food process and process until very finely chopped. Scoop into the same bowl with the cranberries and apple.
Add the sugar to the mixing bowl and stir with a spatula to combine. Taste the relish and add up to an additional ¼ cup of sugar if desired.
Refrigerate for at least an hour, or overnight, and serve cold.