Rathdowney-Errill emerged from the championship opener as nine point winners.
The defending Laois hurling champions have suffered an early set-back.
A meeting of Camross and Rathdowney-Errill promised much before the off and delivered more.
Poor playing conditions didn't prevent entertainment flowing with seven goals and 35 points shared between the two sides.
Camross never fully recovered from a slow start, trailing by six at the break, meaning last year's beaten semi-finalists claimed an early scalp on a final scoreline of 4-21 to 3-14.
In the championship's other group, The Harps face Rosenallis at the LOETB in Portlaoise, while tomorrow Portlaoise and Castletown meet at the same venue.
Both games throw in at 7.30pm.
Shane Lowry Leading The Way At The Irish Open
Alex Dunne Secures Front Row Start For F2 Feature Race In Madrid
Offaly SFC: Semi-Final Spots Up For Grabs
Former Golf Coach Stunned With Stuart Grehan Not Competing At Irish Open
Treaty United The Next Test For Athlone Town
Mark McHugh To Remain In Charge Of Westmeath Footballers
Cannonball 2026 Heading For Offaly Today
Westmeath SFC: St Loman's Mullingar Aiming To Push Forward
Laois SFC: Places In The Semi-Finals Up For Grabs
Shane Lowry Aims To Win Second Irish Open
Laois Soccer Club Plans New Clubhouse And Changing Facilities
Westmeath SFC: Tyrrellspass Secure Survival
Shane Lowry Learns Tee Off Time Ahead Of Irish Open
Walker Cup Victory Loudest Roar I've Ever Experienced - Stuart Grehan
GAA ‘Not Ready’ For Proposed Integration With LGFA And Camogie Association
Offaly SHC: It's Great To Be Back In The Semi-Finals - Brian Duignan
Athlone Town Take Big Leap Towards Defending League Title
Westmeath Photographer Captures Katie Taylor’s Retirement Fight At Croke Park