A decision on the bus strike is due to be made today.
The ballot for Unite the Union members has been open since Friday, and is due to close today at 4.30pm.
The count is expected to take up to an hour, with an announcement being made to the public.
If drivers vote down the proposal, an indefinite strike is planned to begin tomorrow.
Union members have taken part in 10 days of industrial action in recent weeks, over new contracts that were offered by First Aberdeen.
Following a breakdown in talks, both parties agreed to call in independent mediators from the Advisory, Conciliatory and Arbitration Service (ACAS).
The talks with ACAS produced an offer that union negotiators felt could be put to members.