The transport firm carried out an urgent probe amid complaints drivers had been exaggerating length of passenger journeys involving Barrhead residents.
Bosses have passed on new instructions to drivers on the proper use of ticketing machines and the importance of listening carefully to passengers when they board buses and state their destinations.
Pensioner Alex Hosie, 69, from the town's Paisley Road told how he was given a ticket which would have taken him from Barrhead's Main Street to Braehead Shopping Centre, when he was only going across town.
While another pensioner was issued with a ticket for Barrhead town centre to Paisley Cross, when he was only journeying from his home in Auchenback to the United Services Club on Paisley Road.
Three passengers had contacted the News after their tickets did not tally with their journeys.
Passengers voiced concern the extra-milage may put free public travel for the elderly at risk when government is cutting back on public purse expenditure.
And bus firms in Scotland are under pressure to maintain free transport services for pensioners after the £187 million funding pot for the Scottish concessionary travel scheme ran out.
McGill's said it was as concerned about the future of the scheme as concession cardholders and bosses took the issue seriously. A spokeswoman said: "McGill's does not condone overstaging and in the three cases brought to our attention by the News, driver error or additional driver training needs were identified.
"Following the information received from the News regarding these three journeys, written communication was issued to all drivers reiterating the correct use of the ticketing machines and the importance of listening to passengers when stating their destination.
"In addition, McGill's on-street team and newly appointed on-street service delivery manager, will continue to conduct spot checks on drivers and will discuss ticket destinations with all passengers as part of their remit."
The firm added it has contacted Transport Scotland to inform them of these three cases and to request that they reduce any payments to reflect the errors.
The spokeswoman added the firm operated almost a million passenger journeys during the three-week period the tickets were issued to help put complaints into perspective.