The Blues, who are current champions, beat the Scarlets 24-19 at Parc y Scarlets with tries for full back Curtis Povey, lock Calum Haggett and two for prop Keiron Assirratti, outside half Callum Hall adding two conversions.
The Ospreys beat the Dragons 25-5 at St Helens with flanker Mitchell Walsh, No 8 Charlie Davies and Keiran Williams touching down for tries and outside half Phil Jones adding two penalties and two conversions.
Highlights of both these matches will be shown on S4C’s Rygbi Pawb at 5.45pm tonight (Thursday).
Ospreys head coach Steffan Jones, said: “I’m delighted with the victory over the Dragons. It was one of, if not the best performance this season. We were very clinical, the defence was outstanding – despite being stuck on our try line for fifteen minutes in the first half we didn’t concede which was a huge moment in the game for me.
“I’m so pleased with the turnaround in our season. After losing 33-0 to the Blues in November, we have won all our remaining games which is all down to the boys, and has shown great character.
“We’re happy we are through to the final but now we won’t be wholly satisfied until we have performed well in that game and we’ll be going all guns blazing to get the win.”
Richard Hodges, Elite Performance Pathway Manager for the Blues said, “We rediscovered our pre-Christmas form last night after not playing particularly well in the last few weeks. The Ospreys beat us at the Arms Park last week and we won our away fixture so it will be tight.
“We may be champions but the Ospreys are the in-form team at the moment at this level with some quality players in their ranks.
“The final will be on an artificial pitch at Ystrad Mynach which should be to our advantage so we will look forward to a real battle. It will be another chance for our players to put themselves forward for international recognition and selection which is our ultimate aim.”
The WRU Regional Under 16 game between the Dragons and the Blues will take place at 6pm ahead of next Wednesday’s final at Ystrad Mynach.