The global media brief was previously shared by OMD, Publicis Groupe's Starcom network and the Grey-owned MediaCom. McDonald's gave the account to OMD without a pitch.
The £38 million UK account moves out of Starcom Motive. OMD also handles McDonald's in France, Italy, Switzerland and the Nordic regions.
OMD ran the lion's share of the US account, with Starcom handling the children's business. ZenithOptimedia was also on the roster in some of the smaller markets.
Larry Light, McDonald's global chief marketing officer, oversaw the review.
Insiders said the result shocked both the agencies involved and McDonald's domestic marketing departments.
The centralisation follows McDonald's first global ad campaign, "I'm lovin' it", by the Munich-based Heye & Partners, part of Omnicom's DDB Worldwide network.