Premier side Caerphilly scored their first try after only 40 seconds and in five-pointers at will in a 47-0 mauling of Carmarthen Athletic, while Cross Keys winger Mark McGee scored two tries as his side knocked out the Quins
Carmarthen Quins came back from a 9-20 deficit at the break to give Keys a scare, but Giles Thomas' 14 points with the boot were in vain as centre Gareth Chapman's 17th try of the season proved the difference at the final whistle.
Bonymaen ran in four tries as they cruised past Tonna 29-3, with the home backs running in three of their side's four tries to to earn a trip to Newcastle Emlyn in the fifth round.
Blackwood proved too good for Senghenydd, winning 31-7 to earn a fifth-round tie at home to Tonyrefail. Fly-half Jeremy Lloyd continued his great form this season with a 16-point haul in the one-sided match.
Llangefni sneaked past Treherbert 22-12 and are home to Abercynon in the next round, while Premier club Bedwas crushed Narberth 32-7 and advance to a home tie against Llanharan.
Gorseinon held Pencoed tryless in their 18-12 win after coming back from 3-9 at halftime, while Pontypool beat Nantymoel 35-8 and face a daunting trip to League leaders Neath in the next round.
Results: Bedwas 32 Narberth 7, Blackwood 31 Senghenydd 7, Bonymaen 29 Tonna 3, Caerphilly 47 Carmarthen Athletic 0, Cross Keys 25 Carmarthen Quins 19, Llangefni 22 Treherbert 12, Pencoed 12 Gorseinon 18, Pontypool 35 Nantymoel 8.