Bookmaker Coral have installed the former Scotland midfielder as 4/7 favourite to replace Alex McLeish.
The ex-Rangers and Hibernian manager was relieved of his duties, as well as his coaches Peter Grant, James McFadden and Stevie Woods, by the Scottish FA on Thursday.
McLeish has led the side to seven defeats in his 12 matches in charge, including the embarrassing Kazakhstan debacle which saw the side go down 3-0 in the opening game of the Euro 202 qualifiers.
Gemmill was appointed U21 boss in 2016, having previously been installed as the U17 manager two years prior.
Further back in the list are second-favourite Steve Clarke (9/2) and former Scotland boss Gordon Strachan (8/1). Derek McInnes, Craig Levein and Neil Lennon are all among the betting.
John Hill from Coral said: “We have been knocked over with interest in Scot Gemmill ever since we opening betting on the next Scotland manager and on the back of an intense gamble, he is now the odds-on favourite for the job."
Scotland's next fixtures are in June with the Euro 2020 qualifying double header against Belgium and Cyprus.
If Scotland fail to progress from their group they have the Uefa Nations League playoff next year as they aim to reach their first tournament in more than 20 years with some of the games from next year's competition being held at Hampden Park.
Odds to become next permanent Scotland manager:
4-7 Scot Gemmill, 9-2 Steve Clarke, 6-1 David Moyes, 8-1 Gordon Strachan, 10-1 Malky Mackay, 14-1 Derek McInnes, 14-1 Craig Levein, 16-1 Michael O’Neill, 18-1 Alex Neil, 20-1 Neil Lennon, 20-1 Paul Lambert, 33-1 Walter Smith