Groups of Jews not from shevet Levi would work in the bes hamikdash, a week at a time. Their primary responsibility was attendance: being present when korb'nos tzibur, public offerings, were brought. (Source: e.g., commentaries to Taanis 2:7.)
What did these people eat?
For example, did they go twice a day (or so) into Jerusalem to buy food? Did they brown-bag (so to speak)? from home? from a daily or every-other-day trip to Jerusalem? Did they buy food off of the gizbar (treasurer) of the bes hamikdash? Was there perhaps a canteen on the har habayis? Or what? In short, what did they eat?
 Note that the bes hamikdash owned flour and, IIRC, birds that people could buy and use as offerings.