Bath's losing run was extended to five games as Harlequins secured a deserved 28-15 Gallagher Premiership victory at The Rec.
Bath director of rugby Stuart Hooper saw his team hammered 48-3 by Bristol Bears last Friday and they were again well beaten after producing a shocking first-half performance.
Harlequins backed up their impressive win at Wasps with another success thanks to tries from Alex Dombrandt, Aaron Morris and Danny Care.
Hooper must now be fearful for his job because even though Bath scored through Tom Dunn and Tom De Glanville, Harlequins never really looked like losing.
Bath were forced into a late change before kick-off with Josh McNally ruled out.
Ethan Staddon came in for his first start with scrum-half Ben Spencer taking over the captaincy.
Bath fly-half Rhys Priestland and his opposite number Marcus Smith swapped early penalties, but Quins' first try was an absolute peach.
Louis Lynagh, Mike Brown and Care were all involved in the attack.
Brown could have scored, but found Care who popped up to Dombrandt.
Smith improved the effort from underneath the posts before dancing through midfield in thrilling fashion.
Smith continued his fine start with a penalty to put Harlequins 13-3 up, but was then forced off with a blood injury to be replaced by James Lang who immediately kicked three points.
Harlequins were dominant. Dombrandt had a second try ruled out for Joe Marchant blocking the Bath defence from stopping him reaching for the line.
It did not stop Quins wing Morris from soon diving over despite Zach Mercer attempting to scrag him high. Smith did not return, but that did not stop his team.
Bath were awful and on a rare visit to the opposition 22, they gave away a scrum penalty.
Bath wing Semesa Rokoduguni went through a gap at the start of the second half and it looked like Hooper had handed them a rocket at the break.
Hooker Dunn went over from close range and Priestland converted, but any hope of a Bath revival was hit by Rokoduguni seeing yellow for a deliberate knock on.
Care immediately dived over to score and Josh Matavesi joined Rokoduguni in the sin bin for a high shot on the former England scrum-half as he scored. Lang converted anyway.
Going down to 13 men was never going to help Bath although they did at least stay in the fight until Rokoduguni and Matavesi returned to the field.
Harlequins pushed for a bonus-point score in the final 10 minutes and the only disappointment for them on another promising afternoon was the fact a fourth try did not arrive.
De Glanville did grab a late Bath consolation, but the conversion was missed by Tian Schoeman which meant Bath went home with nothing yet again despite incessant late pressure.
