Otago Rugby Football Union general manager Richard Kinley said yesterday Brown was not returning to coach Otago next year and the position would be advertised next week.
Brown (39) joined Otago as its head coach in 2012, signing a three-year contract with the union, and has made some real gains in his time in charge.
Last year, he signed on with the Highlanders as an assistant coach and helped get the franchise into the playoffs for the first time in 12 years.
However, under New Zealand Rugby Union rules, a coach cannot work with a Super 15 franchise and also coach a provincial side.
Brown had to make a choice between the two roles and, logically, picked the Highlanders.
A coach taking on the two roles would face an enormous workload. Pre-season training with a Super rugby team starts in early November with pre-season games in January, followed by a season which does not finish until mid-July at the earliest.
The ITM Cup then starts in mid August and, if a team makes it into the playoffs, it can still be playing in late October.
When professional rugby was in its infancy, a coach could handle teams at both provincial and franchise level, but Super rugby has expanded and squads have got bigger.
Kinley said the search for a new coach would not be limited to just Otago.
''I have had people contacting me already, had worldwide interest, which shows how much the role is valued by a lot of people,'' Kinley said.
''Though Tony is going to the Highlanders, with our blessing, he will still play an important role in Otago and will have our best interests at heart.''
Coaches from outside have not done well with Otago in recent times. Kinley said there would be strong local interest in the role but there would not be any local bias.
He envisaged applications closing by the end of next month. An appointment panel, which had not yet been established, would start looking through applications shortly afterwards.
He said it was likely a NZRU member would be part of the appointment panel.
Kinley said Brown's style of play and attacking mindset were attributes the union wanted to pursue.
''Tony has introduced a style of footy which we want to continue with. All our teams down the grades are trying to play this way. We want the new coach to do the same things into the future.''
Brown emphasised running rugby from the start, and Otago made the final of the championship in 2012 and last year made it to the semifinals before it controversially lost to Hawkes Bay.
The side played entertaining, free-flowing rugby and scored some quality tries.
Brown was also the first coach to steer Otago to a successful Ranfurly Shield challenge for more than 50 years, when Otago beat Waikato last year.
There appears no obvious candidate to take over from Brown.
Assistant coach Phil Young, who has coached Southland, is likely to apply, while other applications may come from the likes of Otago under-19 co-coach Jason Macdonald, who also coached Taieri to the club banner this year, University club coaching director Brendon Timmins, and former Hawkes Bay coach and Highlanders assistant coach Peter Russell.
Otago loose forward TJ Ioane and partner Maua welcomed a baby girl on Saturday morning. Ioane missed the game against Tasman in Nelson on Sunday to stay home for the birth.
