Hibernian are up to second place in the SPL despite being held to a 1-1 draw at home to Dundee United.
Merouane Zemmama fired the home side ahead just before the half-hour mark at Easter Road with an unstoppable drive, but Andy Webster's deflected effort 18 minutes from time meant that the game ended all-square.
Motherwell secured a 1-0 win at home to lowly Falkirk, with Lukas Jutkiewicz heading home the winner from Chris Humphrey's corner with 19 minutes played.
Kilmarnock and Aberdeen drew 1-1 at Rugby Park. A goal from substitute Danny Invincibile 12 minutes from time gave the home side the lead, but Gary McDonald levelled soon after.
Hearts took the lead after half an hour of their trip to St Mirren, with Jose Goncalves heading home following a succession of corners.
However, the home side drew level seven minutes later as Steven Thomson powered the ball home following approach work from Stephen McGinn and Andy Dorman.
Twenty minutes into the second half the Buddies hit the front, as Craig Dargo flashed home a superb volley following Billy Mehmet's flick-on and they held on to earn their first victory at St Mirren Park.
St Johnstone broke the deadlock right on half-time of their trip to Hamilton Academical, with Steven Anderson finding the net from close range following a corner.
A long-range Danny Grainger strike six minutes from time wrapped up Saints' first league win of the season.