Tries from James Buckland, George Stowers and a double from New Zealander Sailosi Tagicakibau helped fire the Exiles to a bonus-point victory at the Madejski Stadium.
Leeds' woes continue as they remain rooted at the foot of the table without a single point to their name after five games.
Northampton kept up the pressure on the league leaders with a hard-fought 27-21 win over Exeter at Franklin's Gardens in a game in which Bruce Reihana passed 1000 points.
Reihana kicked five penalties and a conversion to reach the milestone to keep the Saints just two points behind pace-setters Irish.
Northampton led 16-9 at half-time before Exeter rallied to end the game with a losing bonus point.
Harlequins moved up to fifth place after a late Tom Guest try secured a 23-12 victory over a defiant Newcastle Falcons at the Stoop.
Guest touched down with four minutes remaining to kill off a resilient Falcons team and leave them languishing in 11th spot in the table.
Jimmy Gopperth kicked all of the Falcons' points in horrendous conditions, but Nick Evans scored 13 points with the boot to seal a Quins victory.