This state's classification carries no date range for the species.
Per VT's own statutory game-bird definitions (eRegulations digest, SECONDARY, corroborating VFWD's official statutes): 'Other wild birds including spruce grouse and Hungarian partridge have no open season.' Not mentioned at all on VFWD's own upland-game-birds page, suggesting an extremely marginal/non-established presence in the state.
Confirmed absence: gray partridge has no open season in Vermont, isn't mentioned on VFWD's own upland-game-birds page at all, and no survey of any kind exists -- an extremely marginal or non-established presence in the state.