McRae played in the Scotland A victory over Italy last month as well as in all three matches in the Churchill Cup in June 2006 and against Australia A last autumn.
McRae, a full-back or stand-off, said: "I'm looking forward to next season. I have played against Edinburgh a lot over the years and they play an attractive type of rugby which is one reason I am moving.
"There is also competition for places which can only be a good thing for the club and I'm looking forward to getting there and competing for a place in the team."
Edinburgh executive chairman Alex Carruthers said: "We are delighted to have strengthened the squad, especially ahead of what will be a difficult period, during a world cup year.
"When we took over Edinburgh, we were acutely aware of the size and composition of the squad and these signings will give us significant cover across the backline for next season and beyond.
"The fact they all have sevens experience shows that they have both the required rugby skills allied to pace, which will allow us to play in a manner consistent with Edinburgh.
"This further outlines our commitment to showcase the talents of the best Scottish players from the academy, club and pro game.
"The fact we have also brought Andrew back to Scotland outlines that some players would prefer to ply their trade north of the border in order to enhance their international aspirations.
"All of the players have previously worked with Rob Moffat and this shows the high regard in which Rob is held by the players."
Former full-time sevens player Turnbull is Scotland's highest try scorer on the IRB circuit with 46.
Houston played in Scotland's club international victory over their Irish counterparts at Meggetland last Friday.
Borders apprentice Robertson's try in last season's club international against Ireland at Donnybrook was selected as try of the year at the Scottish Rugby Awards ceremony in May 2006.