Priest was born on June 30, 1961, in Queens, New York. He made his professional debut as a writer in 1983 with the issue #1 of The Falcon miniseries, he was made full editor of the Spider-Man comic books from 1985 to 1986. Due to personal and professional disagreements, he left Marvel. He moved on to write for DC Comics where he had a run as a writer of Green Lantern when the character was exclusive to the anthology series Action Comics Weekly (1988-1989).
Priest worked with numerous artists including Tod Smith, M.D. Bright, and Gil Kane. Owsley wrote two Green Lantern Specials, the second issue concluding the plots left off from the end of Action Comics Weekly, with Bright drawing. They would work again on the first issue of Green Lantern: Emerald Dawn before Owsley departed. He edited several titles in DC Comics’ Impact Comics imprint from 1991 to 1993.
Priest’s work led to him working on series Black Panther vol. 3, Steel, Deadpool and Conan the Barbarian. In 1993, he became part of a group of writers and artists who launched Milestone Media, a comic book publisher affiliated with DC Comics. However, personal problems forced him to scale down his involvement.
He took a break from comics and returned to the writing scene in 2014 after a decade-long absence to write Quantum and Woody miniseries for Valiant Comics. He was later chosen to write the DC Rebirth version of Deathstroke in 2016 and became the writer for Justice League in December 2017. In addition to writing comics, Priest is an ordained Baptist minister, singer-songwriter, and has written several novels.