The Feast of Wine is a Jewish festival prescribed in the Q11 Qumran Temple Scroll, a document found among the Dead Sea Scrolls that describes an idealized temple and its regulations. It seems to have evaded notice of the composers of the Tanakh, hence it was unknown until the 90s Qumran discoveries. They also discovered a Feast of New Oil.
The festival celebrates the new wine on the third day of the fifth month (Av), fifty days after the festival of the First Fruits of grain. On this day, the peoples offer new wine to God "a third from the new wine of each of the 12 tribes" following abstinence from old wine.