Until recently, the oldest remains of feasts by humans came from Middle Eastern sites dating to around 9,500 years ago after farming had been initiated.
Researchers, however, appear to have discovered a cave with evidence of a gathering of 35+ members of the Natufian culture [http://en.wikipedia.org/wiki/Natufian_culture] about the burial pit of a woman who was possibly a shaman. Wild tortoise and wild cattle meat was consumed.
The Natufian people lived from around 15 thousand to 11.5 thousand years ago in the Middle East. Theirs was the first known society to inhabit year-round settlements. The researchers speculate that there may have been a need for community-building rituals, and note that these rituals involved wild plants and wild game that would be later domesticated by people living in the region.
Critics note that the researchers have presented a plausible interpretation of the evidence, but that their conclusions are not air-tight.
The report on the discovery can be found at http://www.pnas.org/content/107/35/15362.abstract?cited-by=yes&legid=pnas;107/35/15362.