Glenavon moved up to fifth in the Premiership table as all their goals came in the second half against a poor Glentoran outfit at the Oval.
The Glens may point to not being awarded a first-half penalty when Eddie McCallion's foul on Niall Henderson appeared inside the box.
Tiarnan Mulvenna put Glenavon ahead from the penalty spot on 53 with Mark Patton doubling the lead on 70.
Youngsters Andrew Hoey and Owen McKeown added further goals on 81 and 90.
Glenavon player-boss Gary Hamilton appeared to be looking ahead to next weekend's Irish Cup semi-final against Crusaders as he rung the changes for the Oval contest.
However, the youthful Glenavon side showed early enterprise and Glentoran keeper Aaron Hogg had to make a fine save to deny Mulvenna.
Hogg had been a late inclusion in the Glentoran line-up as Elliott Morris was ruled out of the contest.
The Glens did appear unlucky not to have been awarded a penalty, instead of a free-kick, as McCallion's challenge on Henderson seemed just inside the box.
Jim O'Hanlon then had another chance for the Glens before the break but his effort was cleared off the line after he had rounded Glenavon keeper Sean McIlhone.
However, the home side collapsed in the second half after Mulvenna put the visitors ahead.
Mulvenna hit the opening goal from the spot on 53 minutes after he himself had been brought down by Mark Clarke and Patton doubled Glenavon's lead on 70 minutes.
Hoey, 17, curled in a great shot from just outside the box on 81 minute and 16-year-old McKeown completed the scoring in injury-time.
Glenavon's win moves them above the Oval outfit in the table.