O'Beirne joined Rocket from the Crypt in 1991 under the pseudonym Apollo 9, shortly after the release of their debut album Paint as a Fragrance. He performed on their second album Circa: Now! (1992), which attracted the attention of major record labels and led to a recording contract with Interscope Records. He also performed in a side project named Rice with Rocket from the Crypt trumpeter Jason Crane (JC 2000). The group, a hardcore punk band with a horn section, also included Carlos Cañedo (of The PeeChees and Beehive & the Barracudas), Dustin "Dirty" Milsap (of Beehive & the Barracudas), and Jason Soares (of Physics, Stacatto Reads, Thingy, and Remote Action Sequence Project). The group sang songs about rice and released one album, Fuck You, This Is Rice, on Lookout! Records in 1992.
In 1995 Rocket from the Crypt had a trio of releases: The State of Art is on Fire, Hot Charity, and Scream, Dracula, Scream!. They filmed several music videos, toured internationally, and experienced a surge of popularity in the United Kingdom. They released RFTC in 1998, but Interscope turned their attention to higher-grossing acts and the band soon left the label. This was followed by the departure of longtime drummer Adam Willard from the group in early 2000. They soon regrouped, signing to Vagrant Records and bringing in new drummer Mario Rubalcaba. O'Beirne continued to record and perform with Rocket from the Crypt, who released Group Sounds in 2001 and Live from Camp X-Ray in 2002. The group disbanded after playing their final performance on Halloween 2005, which was recorded and later released as R.I.P.