"Johnnie Jackson is a player who has always been on our shortlist as a possible loan.
"He's left-footed and everyone knows there is a shortage of good left-footed players around," manager Ray Lewington told the clubs official website.
"He did well on loan at Coventry last season and as well as providing us with another midfield option he can also play left-back and the centre of midfield if needed.
"He's had a taste of life in the Premiership and is a young lad who will be looking to impress."