Before becoming editor-in-chief of Marvel Comics, Harras was chief editor of Marvel's X-Men line. During this time, X-Men-related storylines became very convoluted and crossovers were very frequent, as this was selling books at the time. Harras was also partially blamed for Chris Claremont departing the book after writing it for 16 years. Before becoming an editor, Harras worked as writer on a number of comics, including a run on The Avengers lasting from 1992-1995.
Harras's time as editor-in-chief has been heavily criticized. His tenure was during the time Marvel teetered on bankruptcy around 1996 and 1997 (although the company was already in serious financial trouble when he became editor-in-chief), and his tenure occurred both Onslaught Saga and Heroes Reborn, controversial events that relaunched much of the Marvel Universe with renumbered titles. Harras was also criticized for taking too close of a close hand in the storylines of writers, and preventing writers from being able to tell the stories they wanted to tell. Among the storylines in which he collaborated was the Clone Saga, requiring Norman Osborn to be brought back as the Green Goblin despite the opposition of many of the writers. His decision to relaunch the Spider-Man titles with a revised origin and with the creative team of Howard Mackie and John Byrne was also met with loud disapproval.
During his tenure, Harras oversaw critically acclaimed runs on titles such as Captain America, Daredevil, Ka-Zar and Deadpool, More importantly, Marvel survived, despite the financial threat looming overhead throughout the mid-1990s, and was in better financial shape by the time he left than it was when he became editor-in-chief.
After leaving Marvel, Harras joined WildStorm as contributing editor on November 15, 2001. Harras worked from his New Jersey home office, and reported to Jim Lee, WildStorm's editorial director. He is currently the group editor for DC Comics collected editions.