The Liberal-Progressives were defeated by the Progressive Conservatives in the 1958 provincial election, although Greenlay was re-elected in Portage la Prairie with an increased majority. In the 1959 election, however, he lost his seat to Progressive Conservative candidate John Christianson by 473 votes. Manitoba CCF leader Lloyd Stinson once described Greenlay as "a mild, quiet little man, not lacking in ability but essentially cautious and stubborn". Likeable on a personal level, he was a very conservative administrator. His decision to switch parties in 1950 was met with little controversy.