Ontario Philharmonic (OP) is integral to the landscape of Ontario's classical music scene. OP continues its emergence as one of the most exciting orchestras in the Durham Region/Toronto/GTA areas earning its place among the leading performing arts organizations of the province. OP is comprised of players that are among the finest professional musicians in the GTA and is led by one of Canada's most distinguished conductors on the international scene, Marco Parisotto. OP's early history began in Oshawa, Durham Region, where it was founded in 1957. OP continues to win the acclaim of both critics and audiences.

OP is comprised of up to seventy-five musicians and performs its main concert programs in UOIT's Regent Theatre, Oshawa and Koerner Hall (Telus Centre for Performance and Learning) Toronto. As well, the orchestra performs in various other venues in the GTA. Although the great symphonic and choral/symphonic repertoire is its mainstay, the OP's programs reflect a wide variety of styles from Baroque/Classical/Romantic/Modern to light classical, pop music, jazz and music of the world, in an effort to satisfy the taste of all audiences, diverse cultures, as well as young listeners.

In its earlier years the orchestra was known as the Oshawa Symphony. OP's name was changed in 1995 and again in 2008 in answer to the widening of its audience and its increasing role in providing classical symphonic music to a greater public in the various communities of Durham Region, Toronto, the GTA and other areas of Ontario. Since 2008 the orchestra has been known permanently as the Ontario Philharmonic - a prestigious name fittingly reflecting its impressive development, its service to an area with the major share of the Ontario population, and in homage to the beauty and grandeur of our province.