Leonard joined the club as an elite development player in the summer of 2011, as a graduate of Scotland's international age-grade ranks.
He has started 25 of his 37 appearances in the pivot position and will move south of the border to pursue a position as first choice fly-half at Championship side Leeds Carnegie.
Edinburgh Rugby head coach Alan Solomons, said: "This is the right decision for Harry [Leonard] at this stage in his career, where he will be guaranteed to start at stand-off."
"He has made a good career decision which will, I believe, stand him in good stead in the future."
After coming through the ranks at Galashiels Academy, Gala RFC and the Scotland age-grades, Gregor Hunter began to challenge for a first-team place with Edinburgh Rugby in the 2011/12 season.
He went on to make 16 appearances for the club before injuring his knee playing for Hawick in the RBS Premiership in August, ruling him out for the entire 2013/14 campaign.
A similar misfortune struck Piers Francis who arrived from Waikato mid way through last season.
The Englishman injured his foot in the club's warm up game against Newcastle Falcons at Mansfield Park and has only recently returned to full training.
Speaking of the pair's departure, Solomons added: "It's been a tough year for Gregor and Piers."
"They're both great blokes but unfortunately got injured early in the season and have been unable to play during my time at this club."
"Everyone at the club wishes all three of these players the very best."
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