What was Moshe referring to when he said "v'Osah Nasan lachem Laseis Es Avon ha'Edah"?
Rashi and Seforno: He was referring to the goat of Musaf of Rosh Chodesh. 1
Which they were obligated to eat, in order to attain a Kaparah on behalf of the congregation, and were therefore not authorized to burn it (Seforno).
Why was Moshe upset that one goat was burned? [At most] four Kohanim cannot eat three Chata'os in one day!
Rashi: Their eating brings Kaparah only regarding Se'ir Rosh Chodesh. (They should have eaten it first.)
Toras Moshe (19): They should have eaten at least a k'Zayis [of each] 1 , for then the owners get Kaparah.
Kol Mevaser (2:28:37) infers that the Rambam agrees. Hadar Zekenim (5) asked how four Kohanim (i.e. like the opinion (Zevachim 101a) that Pinchas was already a Kohen) ate four goats, and left this difficult. (Perhaps there is a printing mistake; the text should say 'two goats', or 'how could they eat three goats.' In any case, what is his source that the other goats were totally eaten? Perhaps he holds that the entire Chatas must be eaten for full Kaparah, and if any part was burned, it is as if all was burned! - PF)
Why did Moshe ask why they didn't eat the Chatas "bi'Mkom ha'Kodesh"? They did not eat it at all?