Harlequins condemned London Welsh to their 12th straight Aviva Premiership defeat of the season but not before the bottom side gave them a scare or two.
Wasps' recent improvement continued with a win over Gloucester while there were also post-Christmas Aviva Premiership wins for London Irish, Bath, Leicester, Saracens and Northampton.
England captain Chris Robshaw has been ruled out of Harlequins' European Rugby Champions Cup match against Leinster on Saturday and will see a specialist to examine his shoulder injury.
Harlequins director of rugby Conor O'Shea has backed Nick Easter to continue playing for some time after the veteran number eight inspired a 24-18 Champions Cup victory over Leinster.
Sam Burgess is ready for his Aviva Premiership debut a month ahead of schedule after being named on the bench for Bath's Friday night clash with Harlequins.
Clermont Auvergne, Harlequins, Leinster and Racing Métro were the day's winners as round two of the European Champions Cup ended with four action-packed matches.
Danny Care scored the only try of the game as Harlequins saw off a strong Castres challenge to win the opening match of the 2014/15 European Champions Cup 25-9 at Twickenham Stoop.
European Champions Cup round 1 preview: Saracens boss Mark McCall says that despite his side reaching the final of the Heineken Cup last season, this year's Champions Cup campaign could be an even harder slog.