McDonough, who is currently marketing and R&D director and Ireland general manager at Muller UK, replaces Simon Davies who left last October to setup a marketing agency.
David Preston, who had been doing the marketing job on an interim basis, will now take up the newly created role of director of commercial innovation, and report to McDonough.
Prior to Muller UK, McDonough was German pet care marketing director at Mars and previously worked as a marketing controller at Bacardi Martini.
Molson Coors recently appointed ZenithOptimedia to handle its media planning and buying account. The brewer launched a £3.5m marketing campaign for its Coors Light brand last summer, the brand’s “biggest ever”.
It also signed a four-year extension to its sponsorship of the Carling Cup last year.