The 22-year-old signed a one-year deal last summer with a further 12-month option, but John Hughes has decided to let the attacker find a new club. Greenhalgh sprang to prominence when he won a TV reality show that culminated in him winning a six-month contract in Italy with Inter Milan in 2010.
However, since his return to his the UK in 2012, he has struggled to build his career and was loaned to Stenhousemuir for the final six games of last season.
"We have let him go so he can go find a club," said Hughes. "He has got talent and found himself sitting on the bench here so we felt to further his career, we needed to let him go."