Q. We began reading the torah and realized at the end of the first aliyah that a few people walked out and there was no minyan at the beginning of kriyas haTorah.

What is the correct thing to do? Do we start all over again once the people for the minyan returned? Does the first oleh have to repeat the bracha and the bal korah has to repeat again?

A. In O.C. 58-3, Remah states that even if there was a minyan for the repetition of Shemone Esreh, but they exited before Krias Hatoroh, you cannot begin the reading as it is a different part of the Tefilah. Krias Hatoroh is a Dovor Shebekdusho and it requires a quorum of ten (O.C. 143,1 – Mishna Berura ibid.). In their absence you would have to start over again and repeat with a brocho the first aliyah. If some left after the first reading began (not only the brocho), you could then after the fact, continue without a complete minyan.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a