McIlroy (28), New Zealand's best male bowler, had two comfortable wins on the first day of the Speight's-sponsored event.
He applied pressure in the second half of his game against fellow Black Jack Mike Nagy (Auckland) to win 25-16.
The scores were even at 12-12 midway through the game before McIlroy took control.
McIlroy, who won a bronze medal in the singles at World Bowls in Adelaide in 2012, was untroubled to beat former New Zealand selector Terry Scott (North East Valley) 25-17 in the second round.
He won the prestigious event in 2006, 2008 and 2012 and shares the record of three wins with former international Rowan Brassey (Auckland).
McIlroy is the singles player in the New Zealand team to contest the Asia and Pacific championships in Christchurch next month.
Nagy, who is also in the Black Jacks' five-man team, had a disappointing day and lost both his games.
He was beaten by promising Australian Aaron Wilson 25-14 in the second game.
Wilson (24), the Australian open singles champion in 2013, won a tight first-round game against Terry Scott 25-22.
Dunedin's Mike Kernaghan (North East Valley), who won the event for the second time last year, also won both his games.
He beat Steve Wilson (Dunedin) 25-20 in the first round and North East Valley clubmate Colin Wheeler 25-20 in the second round.
Kernaghan (60) will return to international bowls at the Asia and Pacific championships. He last played for New Zealand 12 years ago.
Australian Brett Wilkie also won both his games.
He beat promising Gore bowler Sheldon Bagrie-Howley 25-15 in the first round and former international Philip Skoglund (Manawatu) 25-19 in the second round.
Mark Casey made it a clean sweep for Australia on the first day when he beat former World Bowls silver medallist Jim Scott (North East Valley) 25-11 in the first round and Andre Smith (Marlborough) 25-16 in his second game.
Other bowlers with two wins were Dan Delany (Auckland), Blake Signal (Stokes Valley), Jamie Hill (Auckland), Sean O'Neill (Timaru) and Tony Grantham (Auckland).
Section play will continue today and the quarterfinals will be played tomorrow from 2.45pm.
