Turnbull's debut professional season was wrecked by injury when he suffered a fracture dislocation of his ankle in September 2008.
But the 22-year-old has since returned to full fitness and this season has featured in 11 games; including three starts in the Heineken Cup.
The second row forward says he is pleased with his progress and now wants to help Edinburgh to challenge for trophies - starting with the Magners League Grand Final in May.
Turnbull said: "I'm delighted to be staying with Edinburgh for the near future.
"At the moment, the club is aspiring to become greater and to win trophies and it is exciting to be part of that development.
"This season has gone quite well, apart from injuring my hamstring over the Christmas period.
"It is just good to be playing some rugby and helping the team to challenge for the Magners League title."
With experienced Scotland locks, Jim Hamilton and Scott MacLeod competing for the two spots in Edinburgh's second row, Turnbull admits establishing himself as first choice is a tough task, but stresses it is a goal that inspires him to improve.
He added: "The level of competition for places in Edinburgh's second row is quite high.
"But I don't see that as being an obstacle - it pushes me on and inspires me to become a better player so that I can earn a place in the team."
Watsonians front row forward Fraser Brown says he is pleased to have earned himself a professional contract and is looking forward to linking up again with Edinburgh head coach Rob Moffat - the man who appointed him captain of the Scotland under-20 team.
Brown said: "I've chatted with Rob and I'm really looking forward to working with him and Tom Smith.
"He showed a lot of faith in me by making me captain of the 20s and now by giving me a pro contract and I want to prove him right."
The 20-year-old hooker has been restricted to just five first team appearances for 'Sonians over the past two seasons after suffering injuries to his neck, shoulder and bicep.
But Brown says he is now aiming to put his injury troubles behind him and he is delighted to have landed himself a place in Edinburgh's professional squad.
He added: "It has been frustrating because I've been hampered with injury over the last couple of years.
"I've had to work through that and now I'm really pleased to have been given an opportunity at Edinburgh."
Local lad McInally, 19, believes his professional deal with his home city team is the pinnacle of his young career so far and he thanked the National Academy and age-grade coaches for helping to achieve that goal.
A former Watson's College pupil, McInally captained Scotland's under-18 team before being fast-tracked through to the under-20 side and now the Watsonians' No8 is entering the professional ranks; something he is incredibly pleased about.
McInally said: "I'm absolutely delighted. I owe a lot to the National Academy for the support work that has come from them.
"I've already experienced being in the Edinburgh environment by working with them on Mondays and Tuesdays and I'm really looking forward to training with them full-time.
"Ever since I joined the National Academy, I've always wanted to play for Edinburgh - it is a dream come true."
Head coach Rob Moffat highlighted the young trio's potential and hunger to learn as being key traits and believes they will all play a prominent role in the long term future of Edinburgh's pack.
Moffat said: "We are pleased that Steve (Turnbull) has agreed a new deal; he is a player with a bright future.
"His first season was difficult because of that serious injury, but the way he responded showed that he has a strong character and he has earned a lot of game-time so far this season.
"Both Fraser and Stuart have shown at under-20 level that they are good players and they both have excellent potential.
"We believe that in the not too distant future they will push the players in their positions in the Edinburgh starting line-up.
"For their age, they are mature, well conditioned athletes and ready to play professional rugby. It will be a challenge for them to earn a starting spot, but their arrivals will create further competition for places in the squad."
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