Originally formed in 1983, My Bloody Valentine had gone through a few lineup changes before they forged a signature sound that was to become known by the music press as "shoegazing" in the late 80s and early 90s.

Along with Kevin Shields' guitar work and Bilinda Butcher's ethereal vocals, Ó Cíosóig's energetic and snare-heavy drumming had become a key element of the band's sound.

As of November 2007, he has reassumed his role in My Bloody Valentine along with members Kevin Shields, Debbie Googe, and Bilinda Butcher.

Ó Cíosóig was credited with "Digital Editing" on Laika's 1995 debut "Silver Apples of the Moon" He formed the short-lived band Clear Spot with Stereolab bassist Simon Johns.

In 2005, he, along with Shields and Sandoval, contributed to Le Volume Courbe's debut album, and he was a guest musician on Film School's 2007 release Hideout.