One appliance and crew from Beaconsfield attended.
Two men, one woman and one boy were out of the cars when they arrived.
The firefighters provided immediate emergency care, before passing the three adults and child into the care of South Central Ambulace Service.
The firefighters used an immediate emergency care pack and an environmental pack.
The road was closed while they worked at the scene.
The incident was left in the hands of Thames Valley Police.
