The custom of eating dairy food on the Shavuot holiday is prevalent among all Jewish ethnic groups, and is one of the festival’s most outstanding identifying marks. Nevertheless, the custom is apparently a late one, first mentioned in Jewish writings from the 16th century. The Sephardic R. Joseph Caro, author of the Shulkhan Aruch did not mention this custom; however, R. Moshe Isserles from Poland wrote: “And in some places it is customary to eat dairy foods on the first day of Shavuot, and it seems to me that the reason for this like the two dishes taken on Passover eve in remembrance of Passover and in remembrance of the festival; thus, a dairy dish is eaten and after that a meat dish.”
Nowadays, it is not customary among Jewish communities to eat two meals (first dairy and then meat!) in the evening; rather, one lavish dairy meal, and more reasons have been found for this. Two meals, as against the two loaves brought to the Temple with the holiday sacrifice. And it is written in Numbers: “...a new grain offering to the Lord at your Feast of Weeks.”