Earls, who was the youngest Lion on the recent trip to South Africa before the arrival of Leigh Halfpenny, scored once in each half as he showed why Sir Ian McGeechan took him on tour despite a lack of experience at the highest level.
O'Connell, meanwhile, was dominant in the lineout alongside fellow Lion Donncha O'Callaghan as Ireland continually disrupted the Welsh throw.
The Munster lock also displayed his under-rated handling skills as his deft offload led to a try for scrum-half Tomas O'Leary.
O'Leary himself was named man-of-the-match 11 months after he was chosen to tour South Africa with the 2009 Lions.
The 25-year-old's Lions adventure may have ended even before it had begun thanks to a broken ankle but, on this form, O'Leary can be expected to be challenging for a squad place once more when the Lions travel to Australia in three years' time.
Ireland's Lions back-row trio of Stephen Ferris, David Wallace and Jamie Heaslip were also superb throughout as the reigning Grand Slam Champions never looked like losing despite having to make double the amount of tackles as the visiting Welsh.
Talk of the town prior to the Croke Park clash was Lions legend Brian O'Driscoll.
The 2005 Lions skipper and triple tourist made his 100th Test appearance for his country, taking his tally for both Ireland and the Lions to 106.
The Leinster star may have had one of his quieter days at the office but his marshalling of Ireland's midfield defence was typically supreme (even if he was penalised more often than usual) and his clever angle set up the first try of the game for Earls.
As for the Welsh Lions, Stephen Jones produced an assured kicking display as he kicked four penalties to claim all his side's points for the day.
The Welsh management of Lions coaches Warren Gatland, Shaun Edwards and Rob Howley will have been pleased to see Matthew Rees return from a nasty groin injury but, like the majority of the Welsh 22, the Lions Test hooker wasn't at his best on a disappointing day for the 2008 Six Nations winners.
Elsewhere on the fourth weekend of the Six Nations, there were obviously no Lions on show when France beat Italy, while those on display in the Scotland versus England clash at Murrayfield failed to light up a largely frustrating encounter.
Former Lions tourist Jonny Wilkinson bagged all England's points in the 15-15 draw in Edinburgh but fellow Lions Mark Cueto, Ugo Monye, Tim Payne, Joe Worsley and Riki Flutey and replacements Lewis Moody and Steve Thompson were unable to break down a water-tight Scottish defence.
For the Scots, 2005 Lion Chris Cusiter led the way at scrum-half, while Euan Murray, Ross Ford and Nathan Hines all played their part but the home side were unable to pick up their first win of the campaign, with a draw a fair result.