Ontario Provincial Police say the crash occurred in Vaughan, Ont., in the eastbound lanes of the highway on the evening of Jan. 14, 2015.
Police say the GO bus struck a guard rail, went into an off-road area and rolled onto its side.
A passenger on board the bus ended up being ejected from the vehicle and became trapped underneath the vehicle.
Radika Nankissoor, 56, of Brampton, Ont., died of her injuries.
The driver and two other passengers were taken to hospital after the crash.
On Monday, police announced that the driver had been charged with careless driving under the Highway Traffic Act.
He is due to appear in court in April.