In 1983, he was appointed Music Director and Conductor of the Santa Barbara Chamber Orchestra. In 1986, Ohyama was appointed Assistant Conductor of the Los Angeles Philharmonic under Maestro André Previn. He held this position for four years and conducted the Philharmonic in many concerts, including subscription concerts at the Los Angeles Music Center, the Hollywood Bowl and the Los Angeles Philharmonic Institute.
Ohyama became the music director of the Santa Barbara Chamber Orchestra in 1983. Four years later, he was appointed assistant conductor with the Los Angeles Philharmonic under André Previn, a position he held for four years and led the orchestra in various concerts at prominent venues such as the Hollywood Bowl.