McGreevey served during the Dominion War in 2375. He was assigned to AR-558, a planet that the Federation Alliance had captured from the Dominion, under the command of Captain Loomis. They were assigned to protect the planet's communication array. Other members of the 150-person unit included Commander Parker, Reese, Crewman Kellin, Vargas and Lieutenant Nadia Larkin.
McGreevey was extremely talkative, and was intensely disliked by his fellow soldier, Vargas, who complained that McGreevey "never shut up". During a battle, McGreevey had been tending Vargas's wound at the time and, as usual, talking. Soon, McGreevey was killed by a Jem'Hadar. The sudden quiet following his death, and the wide-eyed expression he wore, stunned Vargas, deeply affecting him, and he would not allow anyone to change his wound's dressing following the incident as it reminded him of his dead compatriot. (DS9: "The Siege of AR-558")