Margie makes her first appearance as a newly arrived nurse in Requiem for a Lightweight. The episode begins with the P.A. system announcing the arrival of wounded and summoning all personnel to the O.R. Several nurses rush out of the shower tent wrapped in towels. Margie is the last one to do so, and collides with Hawkeye and Trapper along the way. She manages to extricate herself from them but loses her towel while running off. This elicits one of Hawkeye and Trapper's rare salutes. Both Doctors become smitten with her and immediately vie for her affections. However, they both go to Cutler's tent and find her packing her things. Margaret has decided that she is a distraction for the doctors and has had transferred her to another unit. Henry, who is under pressure to put up a boxer for an inter-unit boxer match agrees to bring Margie back if one of the doctors survive three rounds in the ring. The unenviable honor falls to Trapper. With some creative use of ether on his boxing glove, Trapper makes it through the match. Henry brings back Margie as promised - and, of course, she is attracted to Trapper for fighting for her.
For the rest of her appearances, however, she becomes Hawkeye's love interest. Along with Trapper and Hawkeye, Margie would also act as a foil to both Majors Houlihan and Burns, taking part in many of Hawkeye and Trapper's shenanigans.
Her second appearance is in Yankee Doodle Doctor, where she takes part in Hawkeye and Trapper's farcical Marx brothers movie about the 4077th MASH.
In Bananas, Crackers and Nuts, she approaches Hawkeye, offering to spend some time with him as he had asked her out so often without success. However, Hawkeye has been pretending to be crazy in order to qualify for some R&R, so he turns down Margie's advances.
In Edwina, Margie becomes the ring leader of the nurses. Nobody wants to date her friend the nurse Edwina so she organizes all the nurses to reject the advances of the men in the camp until some one agrees to do so. Desperate, the men in the camp draw straws and Hawkeye gets the short one - which amuses Margie hugely.
In Love Story, Radar is all depressed after receiving a Dear John recording from his fiancée so it's now the turn of the men to try to organize a date for him with one of the nurses. Hawkeye approaches Margie in Post-Op but Margie says she is unable as she already has another date for the night. "With whom?" Hawkeye asks. "You!" she replies.
After this, there will be a fairly long break until Ceasefire. Here the camp is jubilant to hear news of an impending ceasefire and everyone's thoughts turn to going home. Meeting Hawkeye in Post-Op, Margie drags him to a private corner and tells him they have to start making "going-home" plans. However Hawkeye rejects her, telling her a lie that he is "suffering from terminal marriage". This earns him a smash on the head with a bed pan.
Ceasefire would be Margie's last appearance. After this, she would be written out of the series with no explanation. Given that Hawkeye had rejected her with a lie, one would imagine any future relationship between the two would be very tense in any case.