Orangeville Music Theatre (OMT) is a non-profit amateur community theatre group that was founded in 1979, originally known as the St. Mark's Choral Society, who presented Gilbert and Sullivan productions to sold out audiences at O.D.S.S. The name was changed to Orangeville Music Theatre when Broadway musicals were produced. The group produces 2 Main Stage shows each year at The Opera House and 2 Youth Productions at Westside Secondary School.