The financial statement for McGill's Bus Services shows turnover grew from £15 million to £27.7m in 2012.
Writing in the accounts the directors - listed as the two Easdale brothers and Ralph Roberts - attributed the increase in turnover to the acquisition of Arriva's routes across Renfrewshire in March last year.
While the exact value of that deal has never been revealed the accounts show McGill's recorded charges totalling £12.4m for the purchase of tangible and intangible assets.
The increase in turnover helped turn around the £552,727 loss reported in 2011 with the accounts recently filed at Companies House showing a pre-tax profit of £659,404 for 2012.
The directors said: "The company has a modern fleet of buses due to continued investment in this area and the directors are of the opinion that the additional comfort which passengers enjoy will increase the company's passenger numbers in future years."
However the directors pointed out trading profitably remains difficult mainly because of fuel costs but said they were committed to running the business as efficiently as possible. The Greenock company employed an average of 589 people across the year, up from 317, which saw staff costs increase from £7.2m to £13.1m. Net debt was steady at £3.7m.
The accounts show James Easdale was owed £326,335, up from £227,425, by the company as an interest free loan with no fixed repayment date.
Alexander, or Sandy as he is known, was due £173,124 which was down from £233,336.
McGill's runs around 350 buses across more than 40 routes covering Inverclyde, Renfrewshire and East Renfrewshire areas.
It is thought to employ around 700 people across depots in Greenock, Inchinnan, Johnstone and Barrhead.
According to the most recent McGill's annual return its entire share capital is owned by Arranglen which is a company majority owned by James Easdale.
James Easdale is a non-executive director at Rangers International Football Club while Sandy recently suggested he has control of around 24% of the proxy votes to be filed before the RIFC annual general meeting later this month.