Bush, 54, was assistant general manager to Jim Hendry, and served as interim GM when Hendry was dismissed in August 2011. Bush, who played on the Twins' two World Series championship teams, helped Theo Epstein in his transition as president of baseball operations one year ago.
The Cubs also announced Louie Eljaua has been promoted to special assistant to the general manager and director of international scouting. Paul Weaver, who was the director, will now be an international cross-checker and coordinator for the Pacific Rim. Alex Suarez was promoted to assistant director of player development.
The team also said Mark O'Neal, the Cubs' athletic trainer since 2004, will stay with the organization but in a different role.
The Cubs named Tim Cossins as the Minor League field coordinator, and were in the process of hiring new Minor League hitting and pitching coordinators.