I search the IFHF's online database at ROOTSIRELAND.IE. It has abt 19 million B/M/D and other records for MOST Irish counties. Records before 1863 are increasingly sparse and almost non-existant before 1800. Many B/M/D events either weren't recorded, or the records haven't survived.
For a James O'Donnell and Susan Doherty marriage in 1866 +/- 1 yr, somewhere in Ireland, I found 3 records: just 1 in 1866, Donegal. This matches your parameters. I also tried to find their parents' forenames without success.
Since this M event occurred after civil registration began, the parents' names are likely on the marriage certificate. You can either try to find this info by viewing the IFHF transcribed record, or contact the General Register Office at WWW.GROIRELAND.IE.