To avoid getting drafted into Army service during the Vietnam War, he enlisted for four years in the U.S. Air Force, including a stint as illustrator in Saigon.

[5] He and Elliot S. Maggin launched the Batman Family title in 1975[6] and Grell would work with Dennis O'Neil on the revival of the Green Lantern/Green Arrow series the following year.

Grell drew All-New Collectors' Edition #C-55 (1978), a treasury-sized special written by Paul Levitz in which longtime Legion members Saturn Girl and Lightning Lad were married.

In this series, Air Force pilot Travis Morgan crash-lands in the prehistoric "hidden world" of Skartaris (a setting highly influenced by Jules Verne's A Journey to the Center of the Earth and Edgar Rice Burroughs' Pellucidar).

For years thereafter, Morgan engages in adventures dressed only in a winged helmet, wristbands, boots, and breechclout, and armed with a sword and a .44 Auto Mag.

First appearing with a cover date of June 1983, Jon Sable was a precursor to what would eventually be called, by some, "the Dark Age of Comics", when even long-established super-heroes would become increasingly grim and violent.

At a convention in the late 1980s, Grell stated that his idea for Sable was "something like a cross between James Bond and Mickey Spillane's Mike Hammer".

During this run, Grell avoided references to the fantastical elements of the DC Universe (e.g., in a guest appearance by Green Lantern the character is out of costume and does not use his powers).

Main character Joshua Brand, the son of a half-Sioux father and an Irish mother, as an adult returns to the reservation he ran away from as a child.

[5] Grell wrote and drew the covers, but did none of the interior artwork, for issues #1–4 of the Shaman's Tears spinoff series Bar Sinister (June – September 1995) from Windjammer,[5] the creator-owned imprint of Valiant Comics.

During this time period, Grell began work writing and penciling the unfinished and unpublished Shaman's Tears/Turok Dinosaur Hunter cross-over limited series for Valiant Comics.

[5] It was during a Grell written story from this period that Tony Stark revealed his secret identity to the world, a development met with mixed fan reaction.

DC sought variant drawings for this story from artists who had worked on the Legion in the past, such as Steve Lightle, Keith Giffen, and Grell.

She ghost-wrote the last two years of The Warlord, while Grell concentrated his efforts on Starslayer; Jon Sable, Freelance; and the weekly Tarzan Sunday comic strip.