By 1933, he was writing for Street & Smith editor John L. Nanovic, contributing short stories to the back pages of The Shadow, Doc Savage, Nick Carter, Pete Rice and others, sometimes under the house name of Walter Wayne.
Donovan wrote virtually the entire first issue of Street & Smith's Movie Action, converting to novelettes such then-current film scripts as Tumbling Tumbleweeds, The Crime of Dr. Crespi, Bodyguard, Powder-Smoke Range, The Last Days of Pompeii, Drake the Pirate and Moonlight on the Prairie under his own name.
In 1935, Nanovic asked him to write Doc Savage novels under the house name of "Kenneth Robeson", alternating with originating author, Lester Dent.
After producing nine Doc Savage novels, Donovan drew on his nautical background to create Captain John Fury for Street & Smith's The Skipper under the house name "Wallace Brooker", after which he also launched The Whisperer, writing as "Clifford Goodrich".
When those magazines folded in the aftermath of the Recession of 1937–38, Donovan continued both characters in the back pages of The Shadow and Doc Savage, and began ghosting the adventures of Pete Rice in Wild West Weekly as "Austin Gridley".
His "Boxcar" Reilly character began appearing in Crime Busters in 1937, as did postal inspectors Joe Bimbo and Howdy Hawks, whom he had originated for The Feds.
After a liquor-induced falling out with John Nanovic in 1938, Donovan moved over to the rival Thrilling Publications, where he began ghosting the adventures of The Phantom Detective under the house name of "Robert Wallace".
The family moved often, residing in Flushing, New York; Southampton, Long Island; and Old Greenwich, Connecticut before relocating to Florida, where they lived in St. Augustine and later, Fort Pierce.