Newcombe founded The Brian Jonestown Massacre in San Francisco, California, in 1990. Core members in the early years included Matt Hollywood, Jeffrey Davies, Joel Gion, Travis Threlkel, Patrick Straczek, Ricky Maymi, Brian Glaze, Elise Dye and Dean Taylor, though the line up was subject to frequent changes. Newcombe wrote the majority of songs, with Hollywood collaborating or contributing others on occasion until his departure in 1998, whereupon Newcombe's name became almost synonymous with the BJM. Newcombe was also heavily involved in the post-production of his albums, often engineering and mixing them on his own. A prolific artist, he authored over 150 songs in a fifteen-year period. The Brian Jonestown Massacre broke up several times since its formation due to differing views and Anton's legendary fights with members of the band/audience. He has been touring the world with a new group of musicians under the same moniker, The Brian Jonestown Massacre.
Newcombe founded his own record label which has released albums by The Brian Jonestown Massacre (Bravery, Repetition and Noise and the re-release of Spacegirl and Other Favourites), The Lovetones' (Be What You Want), and Dead Meadow's (Got Live if You Want It). According to the official website, the purpose of the label is to "...release BJM music not available through other channels, and to record new bands which we will be producing from time to time, while pursuing the goal of making the world unsafe for rock and roll". Many of the releases on this label are produced or engineered by Rob Campanella.