The October 1 closure of the units, which have a combined capacity of 1910MW, follows the shutdown of the 1140MW Lakeview Generating Station in 2005.
The government is in the process of developing a long-term electricity plan that will map out the next steps in the coal phase out. There are now 11coal-fired units at four plants totalling 4484MW still operating in the province.
Ontario was the first jurisdiction in North America to legislate the shutdown of coal-fired generation, which is the single largest source of greenhouse gas emissions in the province.
In 2009, Ontario launched the continent's first comprehensive renewable energy feed-in tariff program to push development of green energy sources.
Speaking about the move, Tim Weis, director of the renewable energy program at the Pembina Institute, a sustainable energy think tank, said: "Sceptics have argued that replacing traditional thermal power plants like coal with a variety of renewable and efficiency options would be impossible, but Ontario's ambitious efforts are proving it is both practical, and technically doable."