In Search of the Brazen Head of Zenopus is scheduled for Sat night from 7-11 PM. The event listing can be found here; currently, 3 seats remain out of 8. This is the same scenario I ran twice last year, including once in the same time slot:
"Meet at the Green Dragon Inn and return to the dungeon under the ruined tower of the doomed wizard Zenopus to search for his legendary talking mask, forty years after adventurers first braved the passages. Play as Boinger, Zereth, Murray, or another character from J. Eric Holmes' stories. This adventure from the Zenopus Archives celebrates the 40+ years of the Holmes Basic D&D set."
Other Gary Con links of interest:
Gary Con website
Gary Con Forums General Discussion
Full Schedule of Events (searchable)
Grand Geneva Resort website
OD&D Discussion thread
Knights & Knaves Alehouse thread
According to the Events schedule, there are 24 games listed as OD&D, including mine.
Other GMs on this list include of the OSR Grimoire blog (2 sessions), Paul Stormberg (3 sessions) and Chicagowiz (1 session), plus 4 from Tim Kask and 1 from Mike Mornard. And Muddy at OD&D Discussion is running three Blueholme games.