For more than an hour there was only a Lewis Bell goal to separate the two sides with hoops keeper Conor Hazard pulling off a couple of vital saves.
During the final quarter Celtic managed to create more chances and showed a real determination around goal with Michael Johnston, Jack Aitchison and Daniel McAllister all finding the net.
“The scoreline looks impressive but I didn’t think that we played particularly well,” O’Halloran admitted. “It took us a while to really get into the game with the goals coming late on.
“Kilmarnock were a better side than Sheffield United (who Celtic beat 4-0 in the final of the Loch Lomond Trophy seven days earlier). We never really got into our stride, never got the passing going and that was frustrating.
“The pitch was a bit sticky but all of the players know that they can perform better. Conor pulled off a couple of important saves before we got among the goals.
“When we created chances we were clinical. Michael Johnston wasn’t at his best but he showed what he is capable of with his own goal and with the run and pass for Jack to score our third goal.
“I was pleased with the fourth, Daniel McAllister was only on the park a few minute and found the net. He scored twice against Fife Elite at the Loch Lomond Tournament then missed out on the final.
“The build up play was good for the fourth goal but you always need someone to convert the chances and Daniel has an eye for goal.”
On Wednesday night, kick-off 5pm at Barrowfield, Celtic open their defence of the Glasgow Cup when they host Partick Thistle.
“We’ve picked the timing of this match to run alongside the Malmo game,” O’Halloran added. “We’ve got our own game to prepare for and look forward to. After that we’ll get along the road for the Champions League qualifier and that’s the target for every player in our squad.”
Celtic have got a team playing in the second tier of the U-17 League with the u-16 squad winning 4-1 yesterday away to Stranraer.
Celtic open their Development League programme tonight hosting Partick Thistle at Cappielow with a 7pm kick off.
CLICK HERE for match report from Kilmarnock