|Portrayed by||Elisabeth Moss|
|First appearance||Smoke Gets in Your Eyes|
|Employer||Sterling Cooper & Partners|
|Residence||Bay Ridge, Brooklyn|
|Romantic Partners|| Pete Campbell (ex-lover)|
Duck Phillips (ex-lover)
Mark Kearney (ex-boyfriend)
Abe Drexler (boyfriend)
Margaret "Peggy" Olson is the copy chief of Sterling Cooper & Partners and previously the copy chief of Cutler Gleason Chaough prior to its merging with Sterling Cooper Draper Pryce. Before obtaining the position at the rival firm, Peggy worked as a copywriter at Sterling Cooper Draper Pryce advertising agency and was considered by its employees as Don Draper's right hand. She started her career at the Sterling Cooper Advertising Agency as Don Draper's secretary.
At Sterling Cooper
Peggy begins work at Sterling Cooper as Don Draper's secretary. She is given a tour of the company by Joan Holloway. With her first day nearly complete, Don chastises her for letting Pete Campbell go through his garbage to find report but tells her that she has a fresh start tomorrow. That night, Pete shows up at Peggy's door, drunk. "I wanted to see you tonight," he says. Without a moment of hesitation, she lets him in.
Peggy begins her job at Sterling Cooper fending off advances from not only Pete but Paul (who later nicknames Peggy "Mouse Ears"); Paul tries to move in on her after giving her a tour of the office and its various departments.
When Pete returns from his honeymoon, he remains conflicted about his involvement with Peggy. Feeling guilty, Pete brings Peggy into a meeting with the creative team. Before joining Harry Crane, Paul Kinsey and Salvatore Romano, he tries to explain that their relationship can not happen. Peggy appears disappointed, but understands.
Because she is aware of Don's frequent "lunch" meetings with Midge Daniels, Peggy mistakes a meeting between Don and Adam Whitman as another encounter with Midge since she is unaware that Adam is Don's brother. Betty arrives with the kids and Peggy attempts to stall them, believing that Don is currently with another woman. Peggy asks Joan to help; Joan covers for Don to Betty. Joan later tells Peggy that she is not happy that Peggy confided in her that Don may be sleeping with other women and that keeping Don's confidences is part of the job.
Pete and Peggy once again become involved, this time as they both end up being the first people to arrive at work. "Do you know how hard it is to see you walking around here everyday?" Pete says, kissing her. Once they have finished, Peggy notices that her collar is ripped. Pete then offers to take a look at her Belle Jolie copy.
Peggy soon begins to gain weight. She splits one of her dresses one day, forcing her to borrow one of Joan's more form fitting dresses. She is brought into a meeting to test a "weight loss" tool, which is a pink plastic belt shaped like women's panties with a small control box and electric cord. She tests it one day, and discovers that it does little for weight loss, but causes a great deal of stimulation.
Pete is not impressed with Peggy's work, and complains to Don; Don retaliates by telling Peggy that she has been promoted to junior copywriter and that Clearasil is her first project. Soon after the promotion, Peggy (who had no idea that she was pregnant) gives birth to Pete's child.
After giving birth to her child, Peggy is kept in the hospital; her state of mind is not what it should be and she remains bedridden and almost comatose. Don visits her in the hospital and gives her advice; this advice bolsters Peggy and ultimately enables her to leave the hospital and resume life. She returns to work with renewed determination. Co-workers speculate that Peggy spent her leave of absence at a fat camp.
A New Company
When rumors of the purchase of parent company of Sterling Cooper reached Don Draper, he pushed the senior partners to attempt a purchase of the company. When that failed, they secretly rounded up a list of clients loyal to them and stole important documentation that would smooth the transition. Peggy Olson, Pete Campbell, Joan Holloway, and Harry Crane were selected as the first employees.
One Year Later
Peggy was working hard as a copy writer a year after the start of SCDP.
One morning Peggy met Joyce Ramsay on an elevator ride. Peggy noticed that Joyce had a pile of rejected photographs and inquired about them. Joyce invited Peggy to a party that her photographer friend is holding downtown. At the party, she offerd Peggy a joint and began to hit on her. "I have a boyfriend," Peggy said. She then was introduced to Davey Kellogg, who was less than impressed with Peggy's suggestion to sell his talent so that he could have money to pursue his art. When the cops raided the event, Abe and Peggy hid in a closet where they shared a kiss.
Months later, Joyce and Peggy go to grab drinks at a bar in midtown Manhattan. Abe had not wanted to visit her at work and thought looking up her home address was odd, so he had Joyce help arrange a second meeting. At the bar Abe criticizes corporations and Peggy's work not understanding that patronizing and belittling a young career woman does not work as flirting. Peggy later pretended she would not have been interested in working on the Barry Goldwater campaign. After being through being insulted, she left. The following day, Abe came to SCDP to apologize. He had written her a story called "Nuremberg on Madison Avenue." After reading it, Peggy asked that he not publish it since it could cost her career. He said that her job was a waste and that she could be so much more, to which Peggy countered telling him that she was not a political person. Defeated, he told her that he would not bother her again.
Joyce and Peggy visit Jones Beach. While packing up the car and preparing to head home, a few other people joined them in the car, including Abe, who insisted he didn't plan their meeting. Arriving back in the city, they headed to her place. Abe and her began to kiss, and spent the night together. He told Peggy that he didn't "usually do anything," after which Peggy told him she didn't want him to leave. Later, he brings by a package to her office, pretending to be a delivery boy. She comes into work late, and only then discovers the problems with losing the Lucky Strike account. 
Around 1965, Peggy thought for sure that Abe was breaking up with her after he asked her to meet up for dinner outside of SCDP to discuss something. In her fear that Abe wanted out, she consulted Joan on what to do and was assured that Abe was going to ask to marry her. Excited, she dressed up nicely for the dinner, readying a yes, only to find out that Abe wanted to move in instead. Trying to hide her disappointment, Peggy said yes and faced the criticisms of her mother only to be assured by Joan that she is being a brave girl and that this is a good thing for her.
After getting a lead from one of Joyce's model friends, Peggy and Stan chase after Topaz Pantyhose. The two met with Topaz and was able to close the account, earning her Don's approval for getting their first client after they lost Lucky Strike.
At Cutler Gleason Chaough
With Don marrying, Peggy's workload at SCDP increases as she basically is now Don's right hand and almost always, he is away spending time with Megan. She's also mentoring Megan on her new copywriter position, which adds to her frustration as Don always whisks Megan away earlier than everyone. Don's treatment of her, and SCDP in general, further deteriorates after she hires Michael Ginsberg, who is equally brilliant and sometimes outshines her, leaving her accomplishments unnoticed.
After meeting up with Ted Chaough who offered her a huge pay raise and a copy chief position, Peggy unconditionally quits SCDP to move to CGC. Don took her resignation calmly and kisses her hand. It didn't take long, however, before she becomes dictatorial as she finds working with CGC copywriters much frustrating than with Stan or Ginsberg back at SCDP.
One late night at work, she receives a call from Stan who gossips to her that Heinz Ketchup is looking to be represented by a new agency, particularly by SCDP, after Heinz Baked Beans, Vinegar, and Sauces division got huge sales boost after the advertising work from SCDP. Ted, eventually picks this information and orders Peggy to start working on a pitch for Heinz.
On the day of the presentation for Heinz Ketchup, Peggy, Ted, and CGC greeted the SCDP team of Don, Pete, and Stan after they finished their presentation with Heinz Ketchup, which didn't quite capture the client's thoughts. Don bids them luck but stays to eavesdrop to Peggy's pitch and finds out that Peggy is using his previous pitch of "changing the conversation." Don realizes that CGC is getting the account and spends the afternoon drinking with the rest of the SCDP team only to be further taunted by Ted who says they got the account, irking Stan who gives Peggy a dirty finger.