Why did Hashem instruct Moshe to cook the Eil ha'Mi'lu'im in the Azarah?
Rashi and Ramban: Because, although a Shelamim is generally Kodshim Kalim (which may be eaten anywhere in Yerushalayim), the Eil ha'Mulu'im is Kodshei Kodshim, which could only be eaten in the Azarah. 1 (and for one day and a night. 2
See Ramban, who is in a quandary as to whether it was a Hora'as Sha'ah that the Basar Milu'im had to be cooked by a Kohen (Moshe), or whether, as the Ibn Ezra explains, Hashem was simply instruting Moshe to see that it was cooked, either by himself or by somebody else - (like we find in Shemos 17:5 and in Melachim 1, 6:14 [Ramban]).
Like the Zivchei Shalmei Tzibur on Shavu'os (Ramban).