So many name variations!

Debbie,

Griffiths Valuation for 1859 lists a Luke Cosgrove in Mullaghglass. He had plot 28a which was an 11 acre farm. (Today that property is off the Ballymaguire Rd). The Valuation Revision records on the PRONI site show the property changing to John Cosgrove in 1873 (suggesting Luke had died then).

I noted some probate abstracts relating to Cosgrove/Coskoran of Mullaghglass:

Coskoran John of Mullaghglass county Tyrone farmer died 5 December 1911 Administration (d.b.n.) Belfast 5 January to Patrick J. Duffy and Robert Creighton farmers. Unadministered Effects £5. Former Grant Armagh 19 April 1912.

Cosgrove otherwise Coskeran James of Mullaghglass county Tyrone farmer died 2 July 1936 Probate Belfast 15 September to Patrick J. Duffy and Robert Creighton farmers. Effects £29.

John’s death:

https://civilrecords.irishgenealogy.ie/churchrecords/images/deaths_returns/deaths_1911/05383/4502501.pdf

The RC parish records start in 1827 so you may be able to trace the family in them.

Debbie,

You can see where the property is located today using Griffiths Valuation.

http://www.askaboutireland.ie/griffith-valuation/index.xml

The site has contemporaneous and modern maps. Use the slider bar in the top right hand corner of the maps screen to switch between the two. As I mentioned in the earlier post, the farm was off what is now the Ballymaguire Rd (which is a rural road a couple of miles south of Coagh). The farm is/was up a dead end lane, just a little to the east of George Hammond’s farm, which is shown on the modern map. The lane doesn’t seem to go right up to plot 28 so I’d infer that that the farmhouse has gone and the land is now part of another farm.  I think the farmhouse probably went out of use in the 1880s. Thereafter it seems to have been land only, according to the Valuation revision records.