St Mirren took a sizeable step towards claiming a place in the Scottish Premiership's top six with a 1-0 home victory over Ross County.

Jamie McGrath stroked home a penalty nine minutes from time to take Jim Goodwin's men four points clear of seventh-placed Dundee United.

County, who struck the crossbar twice, remain in 10th place, just a point ahead of Kilmarnock in the relegation play-off berth.

St Mirren made three changes from the team that drew with Motherwell in midweek. In came Lee Erwin, Dylan Connolly and Kyle McAllister in place of Jon Obika, Richard Tait and Cammy MacPherson.

County made two changes from the side that won against Celtic, with Alex Iacovitti and Callum Morris replaced by Leo Hjelde and Keith Watson.

It was Watson who had the first chance of the game, the defender jumping highest to meet Blair Spittal's corner but unable to get his header on target.

St Mirren responded with a McGrath shot that lacked the power to trouble Ross Laidlaw in the visitors' goal.

Carl Tremarco was first in the book for a heavy and late tackle on Connolly that could easily have been a red card.

From the resultant McAllister free-kick, Laidlaw made a brilliant save from point-blank range to keep out Conor McCarthy's header.

Erwin then slammed a shot well wide of target after being teed up by McAllister.

Play was held up for a while as Joe Shaughnessy received treatment after being caught in the face by Watson's elbow as they contested a high ball into the box.

The defender could not continue after the break and was replaced by Richard Tait, while Hughes made three changes to try to reinvigorate his own side.

Only a magnificent save from Jak Alnwick prevented County from moving in front as the goalkeeper pushed Jordan White's header on to his crossbar. When the ball was recycled to the edge of the box, Stephen Kelly's drive also struck the woodwork.

Both teams used their full quota of five substitutes to try to turn an even game in their favour. And St Mirren replacement MacPherson was quickly called into action to head away White's effort from Harry Paton's corner.

And it was the Saints who took the lead with eight minutes left. Hjelde bundled over Collin Quaner in the box and McGrath kept his composure to convert the spot-kick.

Jordan Tillson could have snatched a draw at the death but his shot dribbled wide and St Mirren held on.