The 2008 champion from Portrush warmed up for next week's Open at Royal Troon by finishing on nine under and five behind winner Alex Noren of Sweden.
McDowell picked up birdies at one, six and 16 but bogeys at 15 and 17 ended his title hopes.
Padraig Harrington was six under after a 71 while Belfast's Michael Hoey was back on four over following a 72.
Noren clinched a one-shot victory over nearest challenger Tyrrell Hatton.
McDowell, who has slipped to 78th in the world rankings, goes into the Open in improved form and having already played two practice rounds at Troon last weekend.
Graeme McDowell carded a final-round 71 to end the Scottish Open at Castle Stuart in joint 10th.