In a 2004 interview with Nathan Ward for American Heritage, Heinz described how he helped Hornberger craft MASH:

“What happened was that a doctor named J. Maxwell Chamberlain helped me write my novel The Surgeon and, previous to that, a Life cover piece about a lung operation. Another doctor, H. Richard Hornberger, had studied under Chamberlain and sent him a letter saying, “That clown who wrote your book might be interested that I have a book I put together from my experiences in Korea.” Betty [Heinz's wife] read it and enjoyed it, which let me know that it was funny – within the realm of decency, once I cleaned it up, since it was full of those jokes that doctors like to make about the body. So that’s the way we got together. Then it took quite a while, maybe a year, back and forth. I eventually tied everything together. As much as it got tied together; there isn’t a hell of a story line in MASH, just a succession of operations and techniques and humor. The only thing that holds it together is the characters and the familiarity that the reader comes to have with them.”

Thus, while not a co-author per se Heinz was responsible for threading together Hornberger’s storylines into a somewhat coherent narrative. Heinz also wrote several novels of his own, including The Surgeon, mentioned above, and Emergency. Oddly enough, included in a 1974 print advertisement in The Chicago Tribune for Emergency is a review quote from Richard Hooker, M.D., “the author of M*A*S*H.”