Q. This year, Shabbos is Erev Shavuos. Since we are going to eat a seuda (meal) of Yom Tov at night, many avoid eating shaleshsudos (the third meal of Shabbos) after mincha, before the shekia (sunset). It is common to divide the seuda after davening in the morning, into two parts. That is, one may wash hands, eat the fish and then bentch, and then wash netila again and eat the cholent, and that will become the shaleshudes meal. How long should one wait between one meal and the other? Should one wait until after chatzos (midday)?
A. On question 1943 we wrote: “Horav Shlomo Miller’s Shlit’a opinion is that on the onset, one should not wait to eat the seuda on Shabbos morning until after chatzos, even if one drinks something before. (Rambam H. Shabbos 30: 9, Kaf Hachaim 291: 2, See Shulchan Aruch 288: 1, Mishna Berura ibid. 1, Piskei Teshuvos ibid. n. 6).
The Rov also maintains that one should avoid on the onset eating two meals, immediately one after the other, as one may incur in the prohibition of reciting unnecessary brochos (Mishna Berura 291: 14 -17) unless one makes a significant hefsek, such as taking a walk outside (ibid.) or waiting at least a half hour in between. (Piskei Teshuvos ibid. n. 50. He quotes a quarter hour )”
The Rov added that the third meal should be lechatchila (on the onset) a half an hour after chatzos, which is the early time to daven Mincha.
Rabbi A. Bartfeld as advised by Horav Shlomo Miller Shlit’a