The decision capped more than a week of speculation that Poston-O’Connor, who had held the post for about 11 months, would be dismissed.
Poston-O’Connor, the fourth person to hold the position since 2004, will receive a nearly $157,000 severance package.
Commissioners Linda Ledbetter, David Richard and Brian Tam voted in favor of the decision, with Chairman Charles Laughinghouse and Commissioner Jim Harrell opposed.
Poston-O’Connor was promoted to the post, which draws an annual salary of $130,000, in September 2007 after serving as interim county manager for about 17 months.
Provided that she was not fired for a felony or misdemeanor involving drug use or gross disregard for moral standards, her severance was to include an entire year’s salary, either in one lump sum or monthly payments.
According to her contract, she could carry over up to 240 hours of compensatory time from year to year, any unused portion of which she could cash in at the end of her employment.
The commission met last week to fire her, but postponed its decision until Thursday.
The delay reportedly was to allow time for Assistant County Manager Doug Derrer and other staff to get up to speed on matters.
Derrer joined the county in January after retiring from Hall County government, where he had worked for more than two decades.
Leading up to the decision, Tam, who voted against Poston-O’Connor’s promotion last year, attributed the situation to what he called a pattern of "withholding information."
Ledbetter had said talk of the dismissal stemmed from the recent discovery that $5 million may have been transferred from reserves without the commission’s authorization.
The shift would have helped cover a $6.9 million shortfall in the county’s budget.