Pour peaches (including syrup) in heavy saucepan. Mix cornstarch in cold water until dissolved. Add to peaches and heat until bubbling. Cook for approx. 5 minutes, until syrup clears and is thickened. Pour into baking dish.
In bowl, mix Bisquick, sugar, and cinnamon. Measure milk in cup, add oil and vanilla and stir until blended. Add to dry mix and stir well. Drop by spoonsful over peaches and bake for 25-30 minutes, until bubbly and crust is golden brown.