The Quins, also unbeaten champions, though of 4 South-West, played sensible rugby and the three drop goals from four attempts helped take them home.
It was strong, competitive and thrilling after the opening half hour had seen only penalties by Quins fly half and captain Gareth Lewis and teenage Mountain Ash pivot Josh Lewis.
Then, the Quins put in their best attack of the game, going left then right and full back Geraint Evans tore over for Gareth Lewis to convert.
A Gareth Lewis drop goal took it to 13-3, but then a brilliant burst by Mountain Ash centre Dale Keepin saw No 8 Chris Edmunds up to score, only for scrum half Lee Ronan to pop over a drop shot for a 16-8 interval lead.
Another 25 minutes of Mountain Ash attack was repulsed until they spread it for full back Gavin Roberts to cross for an unconverted try.
However, the clever Gareth Lewis dropped his second goal before Josh Lewis kicked his second penalty in reply.
After 78 minutes, full back Roberts appeared to score a winning try for Mount, but it was not allowed and even after 12 minutes of time added on, the superb Quins defence refused to yield and the Silver Ball was theirs for the first time since 2001.
Scorers: Maesteg Quins – Try: G Evans. Con: G Lewis. Pen: G Lewis. DG: G Lewis (2), L Ronan
Mountain Ash – Tries: C Edmunds, G Roberts. Pens: J Lewis (2)
