The business was previously split between Mediaedge:cia and Carat. MEC was responsible for handling the £8 million TV buying business and the sponsorship account, while Carat handled radio and press buying, worth £13 million.
MEC led Group M's pitch and the consolidation will also see the Specsavers communications planning, which was previously handled in-house, move to Group M.
The media assignments will be split between MEC's media agencies, with MEC's operations director, Toby Jenner, running the central account management.
Specsavers' marketing director, Andrew Molle, said: "I think this is probably the first example of a cross-media agency group proposition being put together to service a client's needs. This unique solution will ensure Specsavers continues to strengthen its strategic multimedia-channel buying and planning."
Tom George, the managing director of MEC, added: "Under the new arrangement, Team Specsavers will draw on the best talent from across the Group M and WPP portfolio to service every aspect of its communications needs."
Online implementational planning and buying for the brand remains with i-level.