The collision happened at about 3.25pm on Monday in Upper Claverley, near to the Rudge Heath roundabout on the B4176.
It involved a grey Audi A5, which was travelling towards Womborne, and a white Mini Cooper travelling in the opposite direction.
West Mercia Police said that the driver of the Audi, a 62-year-old woman, and her passenger, a 69-year-old woman, were taken to New Cross Hospital, Wolverhampton, with back and head injuries.
The driver of the Mini, a 53-year-old man, was treated at the scene and his passenger, a 52-year-old woman, was taken to hospital as a precaution.
Officers investigating the collision would like to hear from anyone who witnessed it or has dashcam footage which could help them establish how it happened.
Anyone with information is asked to visit westmercia.police.uk/tua/tell-us-about, quoting incident 315 of July 4.