After coming up through the Celtic academy, Michael O'Halloran joined Bolton Wanderers in August 2009, slotting into the U18 side. The striker progressed the youth system and became a fixture in the reserve system at Bolton Wanderers, ultimately being rewarded with three-and-a-half-year contract in February 2012. O'Halloran has not yet made a league debut for the Trotters but was handed a brief first team chance in Bolton's 2-1 Carling Cup win at Macclesfield Town in August, 2012.
Wanderers have sent the young Scottish forward out on loan on three occasions with O'Halloran going to Sheffield United, Carlisle United, and Tranmere Rovers. He scored his first senior goal in a 2-2 draw against Portsmouth for Tranmere. He would ultimately score three times in 23 appearances for Rovers. O'Halloran's Carlisle United loan was supposed to last one month but lasted for all of 12 days after the deal was cancelled.