Date : Seventh day of the month of Pyanopsion (October)
Procession led by , two men dressed as women in ankle length tunics in commemoration of the two youths whom Theseus disguised as maidens to protect the other maidens. They carry vine branches still bearing grapes (oskhoi).The procession starts at temple of Dionysos and arrives at the Shrine of Athena Skira (protectress of the grape harvest). There are cries of Eleleu! Iou! Iou!, a combination of encouragement (Eleleu) and woe (Iou), which recalls both Theseus' return, and the death of Dionysos by which he is reborn.
From Plutarch: The Life of Theseus
The feast called Oschophoria, or the feast of boughs, which to this day the Athenians celebrate, was then first instituted by Theseus. For he took not with him the full number of virgins which by lot were to be carried away [to the Labyrinth], but selected two youths of his acquaintance, of fair and womanish faces, but of a manly and forward spirit, and having, by frequent baths, and avoiding the heat and scorching of the sun, with a constant use of all the ointments and washes and dresses that serve to the adorning of the head or smoothing the skin or improving the complexion, in a manner changed them from what they were before, and having taught them farther to counterfeit the very voice and carriage and gait of virgins so that there could not be the least difference perceived, he, undiscovered by any, put them into the number of the Athenian virgins designated for Crete. At his return, he and these two youths led up a solemn procession, in the same habit that is now worn by those who carry the vine-branches. Those branches they carry in honor of Dionysos and Ariadne, for the sake of their story before related; or rather because they happened to return in autumn, the time of gathering the grapes.
The women, whom they call Deipnopherai, or supper-carriers, are taken into these ceremonies, and assist at the sacrifice, in remembrance and imitation of the mothers of the young men and virgins upon whom the lot fell, for thus they ran about bringing bread and meat to their children; and because the women then told their sons and daughters many tales and stories, to comfort and encourage them under the danger they were going upon, it has still continued a custom that at this feast old fables and tales should be told. There was then a place chosen out, and a temple erected in it to Theseus, and those families out of whom the tribute of the youth was gathered were appointed to pay tax to the temple for sacrifices to him. And the house of the Phytalidai had the overseeing of these sacrifices, Theseos doing them that honor in recompense of their former hospitality.