Lowery, 42, started this week and reports directly to Carolyn Carter, the Grey Global Group EMEA president. He will be based at its London office.
His brief is to bolster Grey's planning offering to multinational clients such as Nokia, Procter & Gamble, Mars, GlaxoSmithKline, Seat and Visa.
He has been charged with recruiting new and promoting existing planners in a bid to improve the network's strategic credentials.
Carter said: "Our clients are looking for big ideas that add value to their brands. John is one of the strongest strategic thinkers in the industry and someone who creative people love to work with. We hired him on his ability to inspire."
Grey's decision to bolster its planning department follows a string of 15 hirings at the creative director level across Europe in the past three years, including Dave Alberts, the executive creative director at the UK agency. Grey Worldwide London recruited its planning director, Dylan Williams, from Bartle Bogle Hegarty last spring.
Lowery describes his role as that of a coach to the heads of planning across the EMEA Grey network, rather than an operational position.
He said his objectives are to increase new business and to improve Grey's contribution to its existing clients.
Lowery was inspired to join Grey by the management team that Carter had installed in London, which is headed by Alberts.
"Carolyn has orchestrated a velvet revolution - I want to be part of that," Lowery said. "Grey is an agency that builds great brands - I want to help raise the game."
Lowery was a Lowe stalwart, working at the agency from 1993 to 2002.
He left the agency following a string of losses, culminating in Lowe resigning the £43 million Orange account.
His departure was part of a restructure that also led to the departure of Lowe's chief executive, Chris Thomas, who was eventually replaced by the present chief executive, Matthew Bull.