Vintage Zen points out that "the story that The Simpsons' creator once illustrated a brochure for Apple back in 1989 has been making the rounds of the internet for awhile now." But until now we've not been able to find actual images of his work for Apple.
At the time, Groening was creating The Simpsons characters, but the show hadn't aired yet, and he was more famous for his comic Life In Hell, which was popular amongst college students. The brochure, titled Who Needs a Computer Anyway is designed in the same style as Life In Hell. Groening worked on Life in Hell all the way up until June 2012.
Apples Who Needs A Computer brochure intertwines typical Apple information with Groening's cartoon illustrations. Vintage Zen points out "was obviously trying to use Groening’s cachet as an underground comic artist to attract hip, young co-eds."
The Simpsons aired on 17 December 1989, which means that Groening was working on this brochure for Apple while creating The Simpsons characters and pitching the show to Fox. This Reddit post of a letter from Matt Groening with an earling drawing of Bart suggests that he was pitching The Simpsons show way back in January 1989).
It turns out that Groening did a lot of other artwork for Apple, including this poster called Networking in Hell, which is also based around is Life In Hell Characters. But before The Simpsons aired on Fox, and became one of the biggest television shows in history, Matt Groening clearly needed to pay the bills and college students in America were treated to brochures and posters from the famed animator.
The headline reads, “Looking for advanced communications between your Macintosh and that ‘Big Blue’ mainframe? Then bring your floppies down to Akbar ‘n’ Jeff’s Communications Hut.”
Website Boing Boing has a quote from former Apple employee Jeff Miller: "Matt Groening did this poster in 1988 for the the networking and communications group at Apple in exchange for a LaserWriter, if you can believe it. David Multer (Akbar) and I were the engineers on MacAPPC, which was a mainframe networking standard championed by IBM. We couldn't convince David to change his name to Akbar, though."
Groening also did this poster titled "Bongo's Dream Dorm" which was a packed illustration of a cartoon dorm adorned with Apple equipment. The tagline is “Macintosh. Part of every students wildest dreams.” Computerhistory.org is also selling T-shirts with this design.
Matt Groening went on from drawing Life Is Hell comics to The Simpsons and Futurama and hasn't designed any brochures for Apple since. He's clearly an Apple fan, however, and Apple has been lampooned in The Simpsons many times and even created an episode called Mypods and Boomsticks that featured the famous Mapple Store.