After being honorably discharged in 1969, he returned home to New Jersey to pursue a career in law enforcement, but a close friend talked him into auditioning for a California-based band called Mourning Reign.

In 1987, former band member Keith Knudsen called Hossack and asked if he would participate in a series of benefit concerts for veterans of the Vietnam War.

Due to the success of these concerts, the Doobie Brothers decided to play together again with band members Pat Simmons, Tom Johnston, John Hartman, Tiran Porter, Bobby LaKind and Michael Hossack.

Since then Hossack's style can be heard on the albums Cycles, Brotherhood, Rockin' down the Highway: The Wildlife Concert, Sibling Rivalry, Live at Wolf Trap and World Gone Crazy.

After months of convalescence and difficult physical therapy, Hossack returned to the band permanently until he developed cancer in 2010 and had to take a leave of absence to focus on his health.