Michael, 26, comes highly recommended from former Edinburgh coach, and current Doncaster supremo, Lynn Howells and the Scotland national team's scrummaging expert Massimo Cuttitta.
On his latest recruit, head coach Sean Lineen said: "Michael Cusack is a fantastic signing for us.
"He is most probably one of the two best scrummaging tight-heads in the English Championship, which is the testing ground in England.
"We've had him up here with Massimo Cuttitta doing a scrummaging session or three and he's phenomenally strong.
"It's the type of guy that we need here and that will add to the competition we have in the front row. This guy really wants to go places, he's very determined."
Cusack came through the ranks at Doncaster as a junior before moving to Leeds where he was part of their Academy system and eventually broke into the senior side.
He moved back to his hometown club in 2008.
Although not qualified to play for Scotland, Cusack will provide the Warriors with a quality front-row option at the start of the 2011/12 season whilst a number of Glasgow players target selection for Scotland's Rugby World Cup squad.
Cusack said: "I really want to make the step up into the Magners League and the Heineken Cup. Both tournaments are a real attraction.
"There a lot of great things going on in Glasgow.
"The facilities at Scotstoun are great and there are a lot of good quality players in the squad - especially with the number of Scottish internationalists the club produces."