Which rival agency does Peggy Olson join after leaving Sterling Cooper Draper Pryce?

The rival agency Peggy Olson joins after leaving Sterling Cooper Draper Pryce is Cutler, Gleason, and Chaough.

By season five, Peggy has grown from Don Draper’s secretary into a highly capable copywriter and the agency’s effective creative leader on several assignments. Feeling undervalued and frustrated by Don’s treatment, she accepts Ted Chaough’s offer to become copy chief at Cutler, Gleason, and Chaough, commonly abbreviated CGC.

Her move is a major professional turning point. Peggy does not leave for a larger real-world agency such as BBDO, McCann Erickson, or Ogilvy & Mather; she joins a fictional competitor led by Ted Chaough, Don’s longtime rival. The decision also changes the balance of power at SCDP, where Peggy’s departure exposes how much of the creative department’s work depended on her.

The separation does not last permanently. CGC later merges with Sterling Cooper Draper Pryce during the pursuit of the Chevrolet account. The combined company becomes Sterling Cooper & Partners, and Peggy returns as copy chief. Thus, CGC is both Peggy’s destination after leaving SCDP and one of the firms that eventually helps form her next workplace.