Bates began submitting ideas for comic book covers to DC Comics at the age of 13, and a number of them were bought and published, the first as the cover to Superman #167 (February 1964). Bates began to sell stories to DC when he was 17.

Bates is best known for his work for DC Comics on such titles as Action Comics, Captain Atom, The Flash, Legion of Super-Heroes and Superman. He began working for the publisher in 1963 and continued to do so up until the early 1990s. His other work includes the comic strips The Lone Ranger (1980—1983), Buck Rogers in the 25th Century (1981—1983), and Disney's Gargoyles during the 1990s. In 2008 he returned after a more than 15 year absence to write True Believers, a limited series for Marvel Comics, about a team trying to get to the bottom of secrets and rumours in the Marvel Universe.

Bates appeared in his own comics several times, along side superheroes like the Silver Age version of The Flash and the Justice League of America.

He also was head scriptwriter on the 1980s-1990s live action Superboy television series, and co-wrote (with Mario Puzo and John Briley) the 1992 film The Discovery, produced by The Movie producers Alexander and Ilya Salkind.

Comics work (including long runs on titles that make it impossible to detail every issue) include:

• Superboy #120, 173 sporadically to 222 (writer, DC Comics, April 1965, April 1971 - December 1976)
• Action Comics #354 sporadically to 581 (writer, DC Comics, September 1967 - July 1986)
• Superman #201 sporadically to 421 (writer, November 1967 - July 1986)
• The Flash #179 sporadically to 350 (writer, DC Comics, May 1968 - October 1985)
• Adventure Comics #381 sporadically to 466 (writer, DC Comics, June 1969 - November/December 1979)
• Vampirella #79 (writer, Warren Publishing, July 1979)
• Jonah Hex #52 and #56 (writer, DC Comics, September 1981 and January 1982)
• V #1 to #6 and #9 to #16 (writer, DC Comics, February 1985 - May 1986)
• Captain Atom #1-46, 50 (writer, DC Comics, March 1987 - February 1991)
• True Believers (writer, with Paul Gulacy, 5-issue limited series, Marvel Comics, September 2008 - January 2009, tpb, March 2009, ISBN 0-7851-2600-7)
• Fantastic Four Cosmic-Size Special (writer, with art by Bing Cansino, one-shot, Marvel Comics, February 2009)
• Last Family of Krypton (writer, with art by Renato Arlem, 3-issue limited series, DC Comics, October - December 2010)