Hi Greg
Irish records back at this point are almost non existant, Irish church registers are now online but not searchable unless you have dates and rarely available before 1800 or later. Belturbet only starts in the 1840s http://registers.nli.ie/ ;
A small piece of the 1821 census for Cavan and I think some of Belturbet area is included, see http://www.census.nationalarchives.ie/search/ believe it or not there are 166 individual O'Haras listed.
There are some OHaras here in the tithes register in Cavan including Templeport http://titheapplotmentbooks.nationalarchives.ie/search/tab/home.jsp ;
There are two OHaras listed on the Flax growers list in Antrim, this was just a list of farmers growing flax.
These County Down sites may assist http://freepages.genealogy.rootsweb.ancestry.com/~rosdavies/ and http://countydown.x10.mx/ and in the general Belturbet area http://www.bawnboy.com/local-genealogy/index.html
Not sure it quite takes in your area. The local paper is the Anglo Celt and some (very little) of its content is onlinehttp://www.irelandoldnews.com/
You might consider writing to the paper which is still in existance but the online phonebook shows no O'Haras in Cavan.
I assumed from the names they were RC religion but if not get back to me and I will give you a link tot the Church of Ireland site which is better for records and slowly putting them online.
Sorry for the delay in responding.
Regards
Pat
