The U16's rounded off the regular WRU Regional Age Grade Championship with a 7-3 win over Newport Gwent Dragons at Ebbw Vale on Wednesday night.
An early try from wing Jordan Adderley, converted by outside half Luke Price, gave the Eyasses the lead, and the Dragons only response in the first half was a penalty shortly before the break.
Conditions deteriorated rapidly after the interval, and with a strong wing at their backs the hosts were able to dominate the second period. However, excellent defence from the Young Ospreys meant that they were able to keep their opponents at bay to secure the win.
They now face the Scarlets in the semi-finals, date and venue TBC, with the winners playing Blues South, who defeated Blues North last night.