Question: I usually hear kiddush in shul after davening on Shabbos morning. Do I need to repeat kiddush before lunch?
Answer: The Shulchan Aruch (OC 273:5) writes that while one is only yotzei making kiddush if it is followed by the seuda, it is sufficient just to eat a little bit of bread or drink some wine. The Magen Avraham (OC 273:10) explains that this is at least a kezayis. The Magen Avraham (OC 273:11) and Mishna Berura (273:25) write that a kezayis of cake will suffice and is preferable to drinking wine. Thus, the Kitzur Shulchan Aruch (77:17) even writes that one making kiddush over cake should use two pieces of cake as lechem mishne, just as one would for any other seuda on Shabbos (See Shemiras Shabbos Kehilchasa 55:4).
The Vilna Gaon (Maaseh Rav 122) and R’ Moshe Feinstein (Igros Moshe OC 4:63), however, hold that as one doesn’t fulfil one’s obligation to have Shabbos lunch without bread, one needs to recite kiddush again before the meal.
Nonetheless, R’ Moshe Sternbuch (Teshuvos Vehanhagos 1:264) writes that while he himself recites kiddush again before the meal, the general accepted minhag is to rely on the Magen Avraham.
R’ Benzion Abba Shaul (Ohr Letzion 2:20:28) and R’ Binyamin Zilber (Az Nidberu 8:31) thus write that if one eats (mezonos) kugel or noodles at a kiddush that is sufficient, too (See Shemiras Shabbos Kehilchasa 52:16; 54:22).In conclusion, providing everybody has heard kiddush, one doesn’t need to recite kiddush again before eating lunch.