Bristol beat Quins 17-3 a week ago, but the west country club's head coach Richard Hill is braced for a backlash.
Hill said: "The word coming out of the Harlequins camp is that they've had a right old beasting this week, particularly on full contact.
"They will bring a highly-motivated squad and will be looking to get their season back on track.
"We will probably have to produce a better performance than last weekend, but we've had an outstanding week of training, so I am happy.
"As a club, it is great that we are still alive in the Heineken Cup because it gives us a bit of an edge and keeps everybody focused.
"We have established ourselves in England over the past couple of seasons, and it would be good to get the Bristol name known throughout Europe as well."
Wing Anthony Elliott, prop Darren Crompton, flanker Joe El Abd and number eight Dan Ward-Smith all gain starts for Bristol, while Quins boss Dean Richards has made numerous changes, with international trio De Wet Barry, Andy Gomarsall and Nick Easter among those who don't feature.