Holders Leinster are six points clear at the top of Pool Three after a win which ended Bath's Heineken Cup hopes.
The province had the four-try bonus point bagged by the first minute of the second half thanks to Rob Kearney, Luke Fitzgerald (2) and Jonathan Sexton.
Scrum-half Eoin Reddan and replacements Rhys Ruddock and Ian Madigan added more tries for the dominant home side.
Bath battled gamely and registered second-half tries through Stephen Donald, Dave Attwood and Ben Williams.
The West Country side had run the Irish province close six days previously but this time had no answer to their opponents' pace and precision.
Leinster's dominance was underlined by the fact that they clocked up 14 unanswered points while skipper Leo Cullen was sin-binned in the first half.
Ireland fly-half Jonathan Sexton finished with 20 points from a try, a superb drop goal and six conversions.
Sexton struck a post with an early penalty but they were off an running in the fourth minute as full-back Kearney dived over from close range after his forwards had driven close to the line.
Barkley chipped over a penalty on eight minutes but Sexton replied immediately with a monster drop goal after latching on to a loose Vesty clearance.
A second Barkley penalty on 15 minutes kept Bath well in touch and they were lifted further as Cullen saw yellow for punching.
But, instead of being put on the back foot, the champions added their second try within two minutes.
When Donald's pass was snatched by Kearney, towering lock Devin Toner set off upfield with the full-back at his shoulder. Fitzgerald was in support to finish off a 60-metre move and Sexton made it 17-6 after 24 minutes.
Still with only 14 men on the field, Leinster emphasised their superiority with a sweet move from deep in their half, setting Fitzgerald free on the left.
Sexton took the inside pass to score in the corner and added the conversion.
Right at the start of the second half, Fitzgerald sidestepped his way to the line and Sexton's conversion made it 31-6.
Sam Vesty went to the bin on 49 minutes for attempting to kill a ruck and it was no surprise that Leinster added a fifth try through Reddan within a couple of minutes.
Bath's plight worsened as hooker Chris Biller joined Vesty in the bin on 55 minutes.
Again it was less than two minutes before replacement Ruddock crossed for the sixth Leinster try.
Donald regained some pride for the visitors with a 63rd minute try converted by Barkley, as both sides made changes.
Bath's doggedness was rewarded with a second try for Attwood and that stung Leinster into action and replacement fly-half Ian Madigan brought up the 50 points with a try converted by Isa Nacewa.
Bath had the last word as Williams crossed and Barkley added his third conversion.
Leinster: R Kearney, Nacewa, O'Malley, McFadden, Fitzgerald, J Sexton, Reddan, van der Merwe, Strauss, Ross, Cullen, Toner, O'Brien, Jennings, Heaslip.
Replacements: D'Arcy for McFadden (53), Madigan for J Sexton (59), Healy for van der Merwe (40), Cronin for Strauss (53), White for Ross (65), McLaughlin for Cullen (59), R Ruddock for O'Brien (53), Boss for Jennings (72).
Bath: Vesty, Cuthbert, Banahan, Barkley, Abendanon, Donald, Claassens, Flatman, Biller, Wilson, Attwood, Caldwell, Louw, Mercer, Taylor.
Replacements: Williams for Cuthbert (56), Heathcote for Donald (68), Cook for Claassens (56), Batty for Biller (67), Beattie for Taylor (53).
Not used: Catt, Perenise, Spencer.
Referee: Romain Poite (France)
Att: 46,365