There were six tries in the first half, including doubles from Ben Cambriani and Tiaan Thomas Wheeler, as the home side raced into a 40-0 interval lead. Four more flowed in the second half as the score built to 66-5.
Iwan Shenton, Ioan Jones, Frankie Jones, Chris Crumpton, Luke Scully and Declan Thomas grabbed the other tries and skipper Scully and Thomas shared eight conversions. The solitary RGC try came at the start of the second half from outside half Harri Jones.
Next up for the young Ospreys will be a friendly fixture against Northampton Saints at the Brewery Filed on Friday, 18 August (kick-off 12.00 pm).