He threaded a neat pass through the Stranraer rearguard for Chris Millar to threaten the away goal, but he was crowded out and Paul Walker, following up, struck his team-mate with his effort.
McLaren made an even greater impact in the seventh minute. Derek Wingate attempted to usher a Millar through ball out for a goal-kick, but Walker robbed him and crossed for the former Dundee United Scottish Cup winner to slam into the net from six yards.
Morton claimed a penalty when a Millar shot struck Fraser Wright, but referee Frickleton ignored all shouts. The visitors came more into the game and Shaun Dillon made a brave block to prevent Stephen Swift from equalising.
Stranraer's Kevin Finlayson had a long-range drive saved by David McGurn, but the Ton keeper had mainly only crosses to field, so shot-shy were the visitors.
The second half was all Morton. Jim McAlistair had a fierce shot deflected away by Murray Henderson and Scott Bannerman just failed to connect at the far post with a cross from McLaren after the classy striker had embarked on a thrilling run down the right flank.
In the 58th minute McLaren strode on to a speculative through ball and, holding off two defenders, stroked the ball under Michael McGovern.
McLaren had a third ruled out for offside and Peter Weatherson fired just wide as Morton continued to dominate until the final whistle.