Powell also did early work for Fox's Wonderworld Comics and Mystery Men Comics; Fiction House's Planet Comics, where his strips included "Gale Allen and the Women's Space Battalion"; Harvey's Speed Comics, for which he wrote and drew the feature "Ted Parrish", (reportedly pencilling at least once under the pseudonym Bob Stanley); Timely's one-shot Tough Kid Squad Comics; Quality's Crack Comics (where he pencilled as Terence McAully), Hit Comics (as Stanley Charlot), Military Comics (where he signed his pencils for the "Loops and Banks" aviation strip as Bud Ernest), Smash Comics (as Powell Roberts), and Feature Comics.
Powell became particularly known for his "good girl art" in Magazine Enterprises' Cave Girl, and in Fiction House's Jungle Comics, where he worked on early Sheena stories and later on the zebra-bikini'd jungle adventuress Camilla.
In the realm of superhero comics, Powell co-created the patriotic character personifying the Spirit of '76, in Harvey's Pocket Comics #1 (Aug. 1941). It would become a long-running feature in Harvey's Green Hornet Comics. Powell also penciled a Golden Age Captain America story, "The Sorcerer's Sinister Secret", in Timely's All Winners Comics #4 (Spring 1942), and pencilled a chapter of the historic All Winners Comics #19 (Fall 1946). He notably drew the backup feature "Mr. Mystic" in Eisner's "The Spirit Section", a 16-page comic-book insert for Sunday newspapers, from the feature's inception in 1940 until Powell entered the U.S. Air Force for his World War II military service in 1943.
In 1961, Powell became art director for the satirical magazine Sick, working there until his death. On a freelance basis, he worked on Topps' 1962 Mars Attacks trading cards, doing the final pencil art based on early pencils roughs by Wally Wood; Norm Saunders then did the final painted art. Powell had previously worked with Saunders and others on Topps' 1961 Civil War News series of cards.
As commentator and columnist Fred Hembeck described Powell's brief tenure at Marvel,
Powell bowed with what was then only the latest — but not last — Giant-Man revamp in Tales to Astonish #65 (March 1965), and was in charge of the exceedingly disappointing meeting between the Human Torch, the Thing, and the Beatles (Strange Tales #130, also March 1965). In all, the former Eisner associate would pencil the final five [Giant-Man] plots (working over [[Jack Kirby|[Jack] Kirby]]'s layouts on the last four), also pencil the last five Torch/Thing duo deals ... did layouts for Wally Wood's last three Daredevil issues ... and would wind up his days at Marvel pencilling two Hulk stories (Tales To Astonish #73 and #74, November and December 1965, both over Kirby breakdowns — one inked by himself, and the second by Mike Esposito).
Will Eisner on Eisner's partnership with Everett M. "Busy" Arnold creating tensions with Powell: "There were problems between partners, because Arnold had his own line of books, and we were sometimes competitors. He offered Bob Powell an increase on what I was paying him for working on 'The Spirit Section', and Bob came to me and said, 'I can make more with your partners.' I called up Arnold and said, 'You want a lawsuit?' Arnold apologized but Powell got very angry, and he said, 'You ruined my career! You cut me off.' I said, 'Well, you want to quit me, and go down the street and work for someone else...well, all right. But you're not going to work for my partner while I'm around'. Anyway, we settled it. When I went into the service ... I got a letter from Bob Powell that said, 'Well, now that you're in the Army, you might get killed. I want to tell you that I forgive you' (laughter)".
Nick Cardy on Powell at the Eisner studio: "Bob Powell came in later when I was doing "Lady Luck". He was sitting behind me. He would help a kid around the block — tell a newcomer to take it easy and that sort of thing".
Will Eisner on Powell at the Eisner studio: "It was a friendly shop, and I guess I was the same age as the youngest guys there. We all got along. The only ones who ever got into a hassle were George Tuska and Bob Powell. Powell was kind of a wiseguy and made remarks about other people in the shop. One day, George had enough of it, got up, and punched out Bob Powell".