|Portrayed by||Aaron Staton|
|First appearance||Smoke Gets in Your Eyes|
|Employer|| Sterling Cooper Advertising Agency|
Sterling Cooper Draper Pryce
|Occupation|| Account Executive|
Former United States Navy
|Other Relations||Cynthia Baxter (fiancee)|
Kenneth "Ken" Cosgrove was an account executive at the Sterling Cooper Advertising Agency. Ken is originally from Burlington, Vermont, was an active duty Navy Seamen and attended Columbia University.
Ken's short story "Tapping a Maple on a Cold Vermont Morning" was published in the "Atlantic Monthly", much to the chagrin of Paul Kinsey and Pete Campbell. Pete, in particular, feels extremely competitive with Cosgrove though Cosgrove doesn't really seem to notice.
Harry Crane discovers that Ken makes significantly more than him, spurring Harry to become the head of the television department.
In 1963, Ken and Pete are pitted for the same role as accounts director. Ken shows himself to understand the clients better, and is promoted, upsetting Pete to such a degree that Pete considers quitting. When Don Draper, Bertram Cooper, Lane Pryce, and Roger Sterling left Sterling Cooper for Sterling Cooper Draper Pryce, Ken was not asked to join them finding out upon return to work the Monday after they left the firm.
Ken made an appearance at the annual CLIO award ceremony. One of his party accidentally dropped a hint that he may be working with SCDP soon. Pete, distraught with the idea that Ken would be working for SCDP again, got confirmation from Lane Pryce that they indeed intended on bringing Ken to the firm. Pete eventually accepted, but made sure that Ken understood that things had changed. Ken jokingly acknowledged this, pointing out that Pete's character had not changed one iota since Sterling Cooper.
Ken was out with his fiancee, Cynthia Baxter, and her parents, when he encountered John Flory an account executive from BBDO. John gave his condolences and moved along. Ken, slightly confused, excused himself from his guests and chased after John, finding out only then that Lucky Strike had gone over to BBDO. Ken immediately apologized to his guests, and went to see Pete at the hospital, where Trudy was awaiting childbirth. He is later seen at a meeting of the entire firm, where they say the company is fine, though all employees must stand firm and try to reach out to new customers.
Ken continued to write at SCDP under the alias Ben Hargrove, writing such stories as "The Punishment of X-4" for science-fiction magazines, before being unveiled at a dinner party at the Campbell household. This resulted in him having to quit, only to start writing again under a new alias Dave Algonquin.