The OMP was founded in 1986, much through the efforts of Dr. Paul Bennett, a former history master at Upper Canada College in Toronto.

OMP was ended after its thirtieth session so that it could be combined with another event to form a larger conference, OMUN.

The annual OMP commences with an "Elections Day", in which the "government" and "opposition" are established.

The students convene at Queen's Park, the legislative building for Ontario.

The students debate their bills as if they were real Members of Provincial Parliament (MPPs).