It was the table-topping Blues North who were always in control on a night when they further confirmed their rejuvenation. They took an early lead courtesy of a try from No.8 Aaron Atkins and a conversion and penalty from the outstanding Dean Gunter.
The Ospreys hit back with an unconverted try from centre Rhys Llewellyn before the break but the Blues totally dominated the second half and scored a further try through the impressive Gunter, which he duly converted.
The Ospreys managed a consolation penalty from Chris Banfield but it was too little too late.
Blues Regional High Performance Manager Gafyn Cooper was impressed with each side, stating: "Both teams tried to play a running game on a heavy pitch and I take my hat off to that."
Blues North now wait to see who they will meet in the Final of the U16 competition.