This ecoregion extends eastward from Manitoulin Island to Kingston at the east end of Lake Ontario in southern Ontario. The ecoregion is characterized by warm summers and mild winters. The mean annual temperature is approximately 6°C. The mean summer temperature is 16.5°C and the mean winter temperature is -4.5°C. Mean annual precipitation ranges 750-1000 mm. The higher precipitation levels occur in areas bordering Lake Huron. Precipitation is evenly distributed throughout the year. The dominant land cover is cropped land with significant areas of mixed forest. Climax vegetation is characterized by sugar maple, beech, eastern hemlock, red oak, and basswood. Pioneer species include white pine, paper birch, and trembling aspen. Moist sites are characterized by yellow birch, white elm, and red maple with slippery elm, black ash, and white cedar occurring in depressions and near streams. Drier sites contain red oak, and white and red pine. The ecoregion falls within the West St. Lawrence Lowland, is underlain by carbonate-rich, Palaeozoic bedrock, and is dominated by a wide variety of deep glacial deposits. Level to undulating bedrock outcropping occurs in a few limited areas. The northeasterly facing Niagara Escarpment, extending northwesterly from Niagara River to the Manitoulin Islands, divides the region into two parts. The area to the west slopes gradually southwestward through an area of rolling topography of low relief. East of the escarpment, the land rises gently from Lake Ontario to Georgian Bay. Loamy Melanic Brunisolic and Gray Brown Luvisolic soils are dominant. Significant inclusions are clayey Gleysolic soils. Characteristic wildlife includes white-tailed deer, snowshoe hare, coyote, red and grey squirrel, and chipmunk. Bird species include the cardinal, wood thrush, screech owl, mourning dove, green heron, pileated and red-bellied woodpecker, and wood and American black duck. The most extensive land use in this ecoregion is agriculture, which occupies 56% of the land area. Mixed, dairy, and cash crop are the dominant farming systems, and major crops include grains, corn, soybeans, hay, and fruit. Other significant land uses include urban development, recreation, and tourism. The major communities include Kingston, Belleville, Peterborough, Oshawa, Kitchener-Waterloo, Barrie, Owen Sound, Stratford, and Brantford. The population of the ecoregion is approximately 2 150 000.
This ecoregion is part of the Mixedwood Plains ecozone.