The Letterkenny side were never really troubled by the Donegal Town lads in Ballybofey as Maxi Curran's men marched into the last four.
At half time Eunan's were 1-6 0-2 up, their goal was scored by Rory Carr and Conor Gibbons kicked four very good points.
The half ended with a mass melee as both teams got involved in bouts of pushing and punching, resulting in referee Connie Doherty booking Karl Lacey and Dara Mulgrew.
Michael Doherty kicked six points in the game for Four Masters but Eunan's rolled out the latter half with points from Donnacha Gallagher, Kevin Rafferty and Rory Kavanagh.
Their second goal was scored by Dara Mulgrew after a mistake by keeper Paul Durcan.
St. Eunan's reach with the semi finals where they will play the winners of Sunday's game between Dungloe and St. Michael's
Meanwhile the county board have confirmed that the replay of Ardara v Naomh Conaill will be played next Wednesday 22nd Oct at 8 pm in Ballybofey.