They joined Merthyr and Swansea in confirming their rise to Welsh rugby's second tier with a 17-8 win over Pontypool.
There is no relegation from the Premiership this season.
Pontypool hope to be among the four teams going up to a division from which there will be no relegation for the next three seasons.
Bargoed have been promoted to the expanded Welsh Premiership for next season.