It is the first time all four brands will be overseen by one person.
In the past they have been handled by separate brand leaders, but an ongoing restructure within the department has seen them moved to other positions.
Reporting to Masterfoods' portfolio director for Europe, Cathy Williams, Oliver will be responsible for strategic and creative development across Europe, and will liaise with roster agencies Abbott Mead Vickers BBDO and Grey Worldwide.
Masterfoods' agencies are appointed at a global level.
Oliver has worked on Galaxy since the start of 2001 and leaves just as the brand is relaunched with swirly graphics on packs and advertising based on the theme 'Think chocolate, think big ideas, think Galaxy'. The revamp will apply to all confectionery lines across Europe.