Impacts of naturally-varying yields on composition and sensory attributes of Ontario Riesling and Cabernet Franc wines were investigated. The sites investigated represented five Vintners Quality Alliance sub-appellations. A grid pattern of sentinel vines was established in each vineyard for data collection. Yields were divided into categories [low, medium, or high (LY, MY, HY)] at harvest (2010, 2011) and replicate wines were made from each. Wines were subjected to sensory sorting tasks to confirm differences between yield categories and sites, and were thereafter subjected to descriptive analysis. All HY vines had higher clusters/vine, berry weights, and Ravaz indices. The HY Cabernet Franc wines had lower colour, anthocyanins, and phenols. Sensory sorting revealed differences amongst wines and descriptive analysis demonstrated several aroma/flavour attributes between yield categories. The HY Riesling wines had less fruit and honey and higher mineral and floral attributes, whereas HY Cabernet Franc wines displayed higher bell pepper, vegetal, and herbaceous characteristics and less fruit attributes. Riesling wines from Lincoln Lakeshore North and Niagara Lakeshore sub-appellations had higher mineral or vegetal attributes, Four Mile Creek had more apple/pear, and St. Davids Bench, Beamsville Bench, and Lincoln Lakeshore South displayed higher fruit and citrus. Escarpment Bench and Four Mile Creek Cabernet Franc 2010 wines had the highest bell pepper aroma, Lincoln Lakeshore North displayed the most earthiness, and Lincoln Lakeshore South had the most cooked fruit. In 2011, cooler sites adjacent to Lake Ontario displayed higher vegetal attributes. Zones of differing yields, dependent upon magnitudes of yield differences, can result in substantially different wine sensory properties.