Guest-starred in 5 episodes on M*A*S*H (1972) as different characters from
1975 to 1982. Two of those episodes were in 1975 alone.
In 1995, Oh founded the Lodestone Theatre Ensemble in response to the
1992 Los Angeles riots that dangerously reignited racial stereotyping.
His continued efforts to present more accurate portrayals of
Asian-American culture on stage has been significant.
He played four roles in the Broadway musical "Pacific Overtures." One
of his roles was as Tamate, a woman, played in Kabuki style. He also
staged the show's martial arts sequences.
His friendly countenance and gentle demeanor made him one of the busiest Asian-American actors over a forty year period from the mid-1960s to the mid-2000s, especially in friendly and sympathetic roles.
Was sometimes mistakenly believed to have been Japanese, due to being born in Japanese-occupied Korea and often playing Japanese characters.
Like other popular Asian actors before and after, although he was Korean, he was often cast as Japanese, Chinese, Vietnamese and even Indonesian.