Yes.

According to the query on the Aiyang Education Network, grapes with s added to the noun are all countable nouns, so grapes are countable nouns.

Vitis vinifera is a tall twining vine with strong anti-cancer properties. The young stems are bare or slightly hairy; the leaves are papery, oval or round; the inflorescences are large and long. The calyx is very small and yellow-green cup-shaped; the style is short and conical.