Shavuos approaches, and as with every Yom Tov food is an integral part of the day. The most well-known food related Minhag on Shavuos is eating Milchigs. However, there are a number of various customs relating to when is best to indulge in the cheese cake. Some families eat one dairy meal and have meat at the other meal, while others start the Seuda with Milchigs and then continue with Fleishigs after a short break. To understand some of the motives behind these varying customs, we must analyze the reasons for eating dairy in the first place.
The most commonly known motive is the one quoted in the Mishna Berura 498:12. He writes there that when the Bnei Yisroel returned home after Matan Torah they were not ready to eat meat. That had just received the Torah and learned that meat requires Shechita with a special knife, removal of forbidden fats and nerves and soaking and salting. All these preparation take a significant amount of time, so for their meal that day they ate dairy item that do not require such extensive measures. In commemoration, we too eat Milchigs. According to this reason, the appropriate time to eat Milchigs should be Shavuos morning.
Based on this logic, it would follow that one should eat an exclusively dairy meal and not follow it with Fleishigs. However, we generally consider a meat meal to be more festive and appropriate for Yom Tov. Furthermore, the morning meal is considered superior to the evening one, and this principle would dictate that if one meal is to be Fleishig, it should be the second one.
The Rama 498:3 cites a different reason for Milchigs. He writes that eating two distinct main courses is similar to the two cooked foods eaten on Pesach, and commemorates the two distinct Korbanos brought on Yom Tov. Furthermore, by having a dairy meal as well as a meat one requires providing new, uncontaminated loaves for the second portion of the Seuda. This reminds us of the two loaves of bread that were the unique Korban on Shavuos. It is an accepted Halacha that a Challa that was eaten from on the table during a dairy meal may not subsequently be used for Fleishigs, and the opposite.
According to this motive, it is clear that it should be necessary to split one of the meals into dairy and meat segments.
The Magen Avraham points out that one must take the appropriately mandated Halachic precautions when splitting ameal. After eating dairy, the bread and tablecloth must be replaced and a period of time waited. Furthermore, one must eat bread or similar food and drink to clean out his mouth. The Zohar dictates that one should not eat milk and meat in the same hour, although many Poskim allow a mere half-hour break. Furthermore, if “hard” cheese is being eaten, many Poskim require a 6 hour wait, similar to following meat.
In conclusion, there is adequate Halachic basis for virtually any configuration of the meals, and each person and family can feel comfortable following their Minhag and their Rav. However, there are reasons behind the various schedules, and a Minhag for a specific one should not be changed lightly. Additionally, one must be familiar with the relevant Halachos to insure no problems are created.