Osoro, 32, a Kenya Army corporal, was shot in the neck by thieves on Sunday night, only hours after being named to the Kenyan marathon squad for the Sydney Games.
The thieves asked him for the keys of his car before shooting him and leaving him for dead. He was rushed to the hospital where he was operated on, medical sources said on Tuesday.
Local police have yet to apprehend the culprits and the stolen car has still not been recovered.
It is now touch-and-go whether Osoro, a former winner of the Chicago Marathon and the 1992 IAAF World cross country overall title winner, will be fit for Sydney.
Once news of the attack became known, the Kenya Amateur Athletic Association moved swiftly to name four athletes as stand-by in case Ondoro fails to recover in time.
The four are 1999 Boston marathon champion Joseph Chebet, Josephat Kibet Kiprono, Benson Ndeti and Nelson Ndereva.
It is not the first time that Osoro has suffered a career setback, having been seriously injured in a head-on car crash in 1995. When he took up marathon running in 1998, he made the fastest-ever debut and set the third fastest mark of all-time to win in Chicago.