A significant number of Roman Catholic Church Records for the province of Ontario has recently been added to FamilySearch website.
As of January 2012, 126,534 records for the Roman Catholic Church for 1760-1923 for what was then known as Upper Canada and Canada West are now available for viewing.
Within the collection you can find baptisms, marriages, deaths and some confirmation records. These records are not indexed but are sorted by county, city/town, and churches.
I personally was quite successful with my own research search this collection.
To find these records enter through the
All records collection link-Canada-Ontario
The records are sorted by the following counties.