AFC Bournemouth have signed Christian Atsu from Chelsea on a season-long loan deal.
Midfielder Miguel Pallardo has signed a new one-year deal with newly-promoted Hearts while Danny Wilson leaves.
Bostock arrived at White Hart Lane from Crystal Palace in 2008 as a highly-rated 16-year-old but has yet to break into the Spurs first team.
He has spent time out on loan at Brentford, Hull City, Sheffield Wednesday and, most recently, Swindon Town.
The 21-year-old will now head out again to gain further experience and he will this time go to Major League Soccer, where he will link up with former Tottenham team-mate Ryan Nelsen at Toronto.
Nelsen was recently appointed as the club's head coach and will be delighted to have increased his midfield options until June with the addition of Bostock.