The East Lothian men put RDVC to the sword at Hallhill in the last eight clash, defeating them 98-5.
The home side used the match to give some fringe players some game time and they did not disappoint. The team ran in three tries in the first 14 minutes through Stuart Crichton, Courtney and Steve Bisset.
Peebles added a fourth before the referee had to retire injured to be replaced by an RDVC official. Two more tries were scored before the interval and it was 38-0 to the hosts.
That lead had stretched to over 50 points as the last quarter approached and in the last 20 minutes the hosts went try crazy.
This gave Courtney and Peebles their four tries apiece, while Gary Peters also scored a nice try and vice-captain Andrew Wightman drove over from close range.
Progressing with Dunbar into the last four are Moray House and Edinburgh Northern.
Moray House won 34-22 against Leith, while Northern won 36-10 at Inverleith.
Dalkeith also look set to progress after their tie with Broughton was postponed.