Seven were taken to hospital after the coach left the A702 near Biggar in South Lanarkshire last night. None of their injuries are thought to be life-threatening.
It wasn't clear what caused the 30-seater bus, operated by McEwan's of Dumfries, to leave the road and end up down an embankment at 8.30pm.
Firefighters were helped by specialist rescuers to reach the 12 passengers and pull them to safety.
A statement from Strathclyde Fire and Rescue said: "The rapid and effective rescue operations carried out by the crews at the scene meant that all persons were removed from the bus within the hour of arrival and casualties were taken to hospital for further check-up.
"The cause of the accident is yet unknown and is being investigated by police."
The bus was in the process of being recovered last night.