Thank you very much for your query. Looking at the spelling for Margaret, could the surname be Traynor?
Do you have any additional information for exactly where Owen died and was buried? You could check newspapers for death notices for that date if you do.
Did you check the marriage certificate for Mary Brady and Owen Murray yet? If not, you might find more details for the exact location her parents were from in Cavan. Again, you have the date Mary Brady died. Check the newspapers and family memorial cards for information.
I hope this of some help. In the meantime, keep an check on the IRO website. Try posting this message on the County Cavan message board: http://www.irelandxo.com/group/county-cavan