Craig Hamilton (Ballochmyle) was pushed all the way by George Robertson (Irvine Ravenspark) before winning through at the first extra hole at Ballochmyle.
Derek Ballantyne (Ardeer) travelled to meet Ian Fraser (Troon St Meddans) and recorded a final hole win to progress to the last eight.
The other remaining third round tie saw Alan Smeeton (The Chase) play host to Tony Fraser (Annanhill) with Smeeton going through with a 4 & 3 win.
The full draw for the quarter finals, to be completed by 28th July, is :-
CRAIG HAMILTON (Ballochmyle)
BERT FERGUSON (Troon Welbeck)
ANDREW JESS (Ayr Belleisle)
DEREK BALLANTYNE (Ardeer)
IAIN McKENZIE (Largs Routenburn)
STEVEN McEWAN (Holder - Caprington)
RYAN SMITH (Prestwick St Cuthbert)
ALAN SMEETON (Chase)
The semi finals will be played at Royal Troon on Friday 2nd August with the final, also at Royal Troon, on Friday 9th August