[5] Berkey worked as a freelance artist from the 1960s, after an eight-year stint at Brown & Bigelow, a St. Paul, Minnesota, advertising agency.

[6] Among other commissions, Berkey regularly produced artwork for magazines such as Popular Mechanics, Omni, Science Fiction Age, Discover, National Geographic, TV Guide and The Plain Truth.

[6] Following this success, he went on to design a large number of book covers including works by Isaac Asimov, Ben Bova, Philip K. Dick, Robert Heinlein, Glen Cook and many more.

For the 1972 edition of Asimov's novel, The Caves of Steel, Berkey's cover art featured a self-portrait with his arm showing exposed cybernetic mechanics.

This established Berkey's reputation and he went on to produce poster artwork for a number of other blockbuster films including the 1976 remake of King Kong, Orca the Killer Whale (1977), Meteor (1979), Black Stallion (1979), Superman III (1983), and Dune (European release, 1984).

[11] It is thought that this painting in particular had a strong influence on the production design of Star Wars and served to inspire the film's leading concept artist, Ralph McQuarrie, and the model maker Colin Cantwell, whose early designs for the Death Star battle station bore a strong similarity to Berkey's painting.

Among this work was a painting which depicted the character Luke Skywalker brandishing a lightsaber, flanked by Princess Leia Organa the robots C-3PO and R2-D2, and a number of Imperial stormtroopers; in the background is a large figure of Darth Vader looming behind them, a similar composition to the theatrical poster artwork for Star Wars by Tom Jung and the Brothers Hildebrandt.

The painting was issued as a souvenir poster that was included in the first release of the Star Wars Original Motion Picture Soundtrack by 20th Century Records.

[13][15][3] Berkey's involvement in Star Wars was brought to an end after a conflict of interest with his work for rival film studio Universal on the 1978 TV series Battlestar Galactica.