Q. Can a fleishig siyum be made if each one in the group learned only a few dafim leiluy nishmas a friend and then they joined for the siyum?

A. The source for celebrating the conclusion of the study of a tractate of the Talmud is found on the tractate Shabbat (118b): Abaye said: “May I be rewarded for that when I saw that a disciple had completed a tractate, I made it a festive day for the scholars”. I would seem from this saying that we are considering the study of an entire tractate by at least one individual, although many may be learning together. Igrois Moishe (O.C. 1:157) proving why we may do a siyum banquet on the termination of a mitzva that involves a lengthy time span, quotes the Talmud and Rashbam in Baba Basra (121). It mentions that the 15 day of Av was considered a day of rejoicing, as it marked the conclusion of the cutting of the wood needed for the altar. Igrois Moishe explains that it was not made a compulsory day of celebration or a occasion that requires a seudas mitzva, since no single individual cut the whole wood supply required, rather it was done by many.

Horav Shlomo Miller’s Shlit”a opinion is that indeed, we require at least one individual to complete the whole tractate, and then the many who are friends or related acquaintances, may join for the seudas mitzvah.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a