Leeds Carnegie have built a seven-point lead heading into their semi-final second leg after a first victory of the season over London Welsh at Headingley Carnegie.
Glyn Hughes scored 25 points with the boot, notching seven penalties and two conversions from nine attempts.
Rob Vickerman and Fred Burdon scored the tries in a game in which Leeds never trailed.
Andy Awcock scored a try either side of half-time as London Welsh showed their strength, and they also were awarded a penalty try.
The second leg is next Sunday at Oxford’s Kassam Stadium.