Q. Since Tu Beav is such a great Yom Tov, does one have to eat meat and drink wine on that day?

A. Indeed, Minhagei Maharil (H. Taanis 11) writes that on a certain occasion Mahari Segal decreed that one should not eat meat during all Mondays until the Yamim Noraim,. On that year Tu Beav fell on a Monday and Mahari Segal ruled that on this particular time, although Tu Beav is a Yom Tov and normally one should eat meat, that year was different.
On question 850 in regards if there is an inyan to make in our days a siyum on Tu Beav since it is considered one of the greatest Yomim Tovim, we wrote
The Mishna (Ta’anis 26b) quotes Rabban Shimon Ben Gamliel saying that; There were no greater Yomim Tovim than the fifteenth of Av and Yom Hakipurim. Most of the six reasons mentioned in the Talmud (ibid 30b, 31a) for the greatness of joy on Tu Beav apply only in the days of the Beis Hamikdosh, (Gevuros Ari ibid), therefore some Poskim maintain that you may even fast on Tu Beav. (Shibolei Haleket 30.) However, our custom is to consider the day as a minor or partial festivity and not to say Tachanun (Shulchan Aruch O.H. 131: 5) or fast. (see next question.) It is also apparent from the Midrash (P’sichta Eicha Rabbasi) that after the churban the simcha and joy of the day ceased. (See also Mishna Berura 131: 30)
Nitei Gavriel (Ben Hametzorim 2: 98: 13) mentions that some (Bais Aharon – Minhagei Karlin p. 8, Darkei Chaim Vesholom 683 on Munkatcher traditions) would make a seuda on Tu Beav. However it is not a common custom..
Horav Shlomo Miller’s Shlit’a opinion is that one should maintain the minhagim and traditions of his community and family.

Rabbi A. Bartfeld as advised by Horav Shlomo Miller Shlit’a