After spending six months in the Swiss army and dropping out of Berne University, Frey moved back to Britain and started a two-year course at the London Film School, during which he supported himself with freelance work, including illustrating War Picture Library comic books. As a child Frey had loved The Eaglecomics magazine, and as an adult worked on the 1980s revival, drawing the strip Dan Dare. Also during the 1970s, he illustrated for IPC Media's Look and Learn magazine, including the strip The Trigan Empire. He was commissioned to create 1930s-era comic book art for the pre-title sequence of the 1978 movie Superman. Through the late 1970s and the 1980s Frey was a prolific creator of gay erotic art, usually published under the pen nameZack. These included a comics series featuring a big, muscular bad-boy hero named "Rogue" for HIM Magazine, a monthly gay male pornography publication which he and his partner Roger Kean owned, along with related titles. He also produced, edited, and illustrated several issues of Man-to-Man Magazine. Frey illustrated twelve of the HIM Libraries, the first two written by Kean, the remainder by various authors who submitted manuscripts. The company was raided by the police in 1981, and all of its stock was destroyed under then-current laws. His gay pornographic work was also featured on front covers and in volumes of the Meatmen series of gay erotic comics. Russell T. Davies, writer of the British television seriesQueer as Folk, praised Frey's serial "The Street" as an important influence on his ground-breaking gay TV drama. When Roger Kean and his brother Franco founded the computer magazineCRASH in 1983, Frey became the magazine's illustrator. He went on to illustrate for CRASH's sister magazines Zzap!64, Amtix, and The Games Machine. He illustrated the comic strip "Terminal Man", written by Kelvin Gosnell, which was serialized in both CRASH and Zzap!64 in 1984, and published as a complete story in a large format book in 1988. During the late 90s, Frey worked as publishing director for Thalamus Publishing in Shropshire, which specialized in illustrated historical reference titles. Thalamus Publishing went into receivership in August 2009. Frey and Kean formed Reckless Books in Ludlow, specializing in young adult action-adventure, historical, and gay adult reading. Several of Frey's painted front covers for Fleetway and IPC War Picture Libraries were reproduced from the original art in two of David Roach's books, Aaargh! It’s War in 2007, and The Art of War in 2008. Frey is the illustrator of over 16 books under the name Oliver Frey and over 12 under the pseudonym Zack. Classic video gaming magazine Retro Gamer has featured Frey's artwork on its cover. In July and August 2014 his gay erotic work was included in an exhibition at the British Library, where he was interviewed by novelist and reporter Rupert Smith. Frey sells signed prints and paintings, and takes private commissions.
