In 1977, during a finance class at BYU, Bagley doodled a political cartoon, which he submitted to the student newspaper, The Daily Universe. This became his first published cartoon, which was reprinted in Time Magazine just weeks later.
After graduation, Bagley briefly worked as a caricaturist in the nearby Orem Mall, before being hired as the editorial cartoonist at The Salt Lake Tribune, where he still produces a daily cartoon. His cartoons have appeared in The Washington Post, The Guardian of London, The Times of London, The Wall Street Journal, Newsweek, and The Los Angeles Times. Over the years, he has produced more than 10,000 cartoons for the Tribune.
Balgey is syndicated and his work is regularly featured at Daryl Cagle's Political Cartoonists Index (Cagle.com). He is also an illustrator and author of independent political cartoons and children's books. His liberal political stance contrasts with the conservative state of Utah, and has influenced several books of political cartoons and humor, including 101 Ways to Survive Four More Years of George W. Bush, Clueless George Goes To War!, Clueless George Is Watching You!, and Clueless George Takes on Liberals!.
In 1992, Bagley received the Wilbur Award for Religious Communication from the Religious Public Relations Council for a cartoon in the April 23, 1991 Tribune. He was the first cartoonist to receive the award, which is given for "outstanding communication of religious values in the news and entertainment media."
Bagley's 2002 book Dinosaurs of Utah and Dino Destinations was nominated for the Utah Children's Book of the Year.
Bagley was the recipient of the 2007 Torch of Freedom Award from the American Civil Liberties Union of Utah. Bagley was awarded the 2009 Herblock Prize for editorial cartooning by a unanimous panel of judges, made up of Garry Trudeau, Jules Feiffer and John Sherffius, representing the Herb Block Foundation.