As editor, O'Halloran worked on the short drama Eviction (2004, with Dan Curry, Armin Shimerman, and editor Harry Jierjian), the webseries Battlestar Galactica: The Resistance (2006) and Battlestar Galactica: The Face of the Enemy (2008), and Ronald D. Moore's science fiction series Battlestar Galactica (2006-2009, with producers David Weddle and Bradley Thompson). In 2009 he received an Emmy Award nomination for Outstanding Single Camera Picture Editing for a Drama Series for the Battlestar Galactica episode "Daybreak, Part II", shared with fellow editors Andrew Seklir and Julius Ramsay. Also in 2009 he was interviewed for the Battlestar Galactica DVD special Evolution of a Cue along with Ronald D. Moore.