Which portion of the Torah is read on Rosh Chodesh?
On Rosh Chodesh, the "head" of the new month, we read four aliyahs from Numbers 28. The requirements for any aliyah is a minimum of three verses. In Numbers 28, along with the daily and weekly Temple sacrifices, we read of the special offerings brought in honor of Rosh Chodesh. Here is the aliyah breakdown:
First aliyah (Kohen): Numbers 28:1-3
Second aliyah (Levi): Numbers 28:3-5 (No, that was not a mistake, we do read verse 3 twice.)
Third aliyah: Numbers 28:6-10
Fourth aliyah: Numbers 28:11-15
Please let me know if this helps.
Rabbi Menachem Posner