At Tondu the home club scraped home by 21-20 in the all Division OA fixture with Pontardawe.
In nearby Kenfig Hill, a young Carmarthen Athletic team held the advantage over the home team and won 23-13.
An experienced Merthyr team travelled to Kidwelly and were beaten by another young team in an excellent encounter by 18-10.
The draw for the Semi Finals to be played on neutral venues on 14th April will be:
Glamorgan Wanderers v Tondu
Kidwelly v Carmarthen Athletic