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's professional growth included his appointment as Music Director of the Santa Barbara Chamber Orchestra in 1983. He then assumed the position of Assistant Conductor with the Los Angeles Philharmonic under André Previn, a role he held for four years and demonstrated his expertise through performances at prominent venues such as the Hollywood Bowl.