This is the earliest version I can find with Google Books. It has only 3 verses. Does anyone know of an earlier published source?

From an article "Ballads of 1916" by Donagh Macdonagh in The Bell (Dublin: Vol. 2, No. 1, April, 1941), page 29:

[No title or attribution is given.]

As down the glen one Easter Morn to a city fair rode I,
There armed lines of marching men in squadrons passed me by.
No pipe did hum, no battle drum did sound its dread tattoo,
But the Angelus Bell o'er the Liffey swell rang out in the Foggy Dew.

Right proudly high over Dublin Town they hung out the flag of war,
For it's better to die 'neath an Irish sky than in France or in Sud-el-Bar,
And from the plains of Royal Meath strong men came hurrying through
While Britannia's sons with their great big guns sailed in with the Foggy Dew.

'Twas England bid our Wild Geese go that small nations might be free,
But their lonely graves are by Suvla's waves or the shores of the wild North Sea,
Oh, had they died by Pearse's side, or fought with Cathal Brugha,
Their graves we would keep where the Fenians sleep 'neath the hills of the Foggy Dew.