The defender broke into the Kilmarnock side last season at just 16 and went on to make his first start in Killie's famous 2-0 win over Celtic at Celtic Park last October.
O'Hara made 20 appearances in all competitions last season and his form at Rugby Park caught the attention of a host of clubs south of the border.
Everton are thought to have watched the full-back in action last season, while several Premier League and Championship sides are believed to be keeping tabs on his progress.
The versatile defender, who does not turn 18 until December, is regarded as one of the best young prospects to emerge in Scotland in recent years and is tipped for a big future in the game.
Kilmarnock are reluctant to lose O'Hara, but are braced for offers for the full-back if he continues his rapid development.