James Dayton netted with a superb strike as Kilmarnock beat St Mirren at Rugby Park.
Cillian Sheridan headed his first Killie goal to put the hosts ahead against the run of play.
St Mirren's Lewis Guy had earlier been denied twice in quick succession by keeper Kyle Letheren.
The hosts took control after the break with James Fowler firing a second and Dayton hammering into the top corner before Paul McGowan's late consolation.
The Rugby Park side now join the Buddies on nine points after seven matches.
Kenny McLean lifted a shot over the Kilmarnock crossbar early on before Michael Nelson came even closer for the hosts with a stinging low drive that skimmed the outside of the post as St Mirren struggled to deal with a corner.
A dithering Manuel Pascali gifted possession to McGowan, who sent Guy clean through on Letheren's goal but the stopper made an excellent save.
And Letheren was Kilmarnock's saviour again moments later after more carelessness in possession allowed Guy in to try and round the keeper, the Welsh keeper got a strong hand on the ball before Steven Thompson blazed the resulting loose ball high wide.
Killie were struggling to get a foothold in the game and there was more frustration for the home fans when a promising break involving Sheridan was halted by a handball by Marc McAusland, who was booked.
But Killie then capitalised on slackness by St Mirren as Jim Goodwin conceded possession and the ball was worked out to Danny Racchi, whose superb cross from the right was crisply nodded into the net by Sheridan.
St Mirren tried to re-assert themselves and Paul Dummett was denied by Fowler's clearance near the goal-line after Letheren had failed to gather a high ball.
Kenny Shiels' side remained a threat on the break and Dayton escaped Goodwin before crossing for Harkins to head wide.
And they extended their lead as another Racchi cross bounced back off Sheridan to Fowler, who buried the ball past Craig Samson.
Dayton had looked dangerous on Killie's left and he got his reward for an enterprising display when he cut inside his man and unleashed a powerful angled shot beyond the reach of Samson.
That forced St Mirren manager Danny Lennon into action, he made a triple substitution with Thompson, McLean and David van Zanten making way for Sam Parkin, Dougie Imrie and David Barron.
And the changes did give the visitors fresh attacking impetus as Guy struck the bar from McGowan's delightful chipped pass but Parkin could not convert the rebound.
Dayton and Harkins were given a standing ovation from the home fans as they came off to be replaced by Rory McKenzie and Chris Johnston.
McGowan eventually found the net for the visitors, the former Celtic player driving low past Letheren from Parkin's headed knock-down seven minutes from the end.
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Live Text Commentary
Full Time The final whistle is blown by the referee.90:00 +3:35
Gary Teale takes the outswinging corner, Close range header by Sam Parkin goes over the crossbar.90:00 +3:03
Dougie Imrie takes a shot. Liam Kelly gets a block in.87:19
Effort on goal by Chris Johnston from just inside the box goes harmlessly over the target.87:00
Centre by Rory McKenzie, clearance by Paul Dummett.86:10
Sam Parkin challenges Manuel Pascali unfairly and gives away a free kick. Kyle Letheren takes the free kick.84:53 Booking
Booking Booking for Danny Racchi.84:35
Foul by James Fowler on Dougie Imrie, free kick awarded.83:53
Corner taken by Dougie Imrie from the left by-line, clearance made by Kyle Letheren.82:42 Goal scored
Goal! - Paul McGowan - Kilmarnock 3 - 1 St Mirren Goal scored by Paul McGowan from just outside the box to the bottom left corner of the goal. Kilmarnock 3-1 St Mirren.82:30
The ball is sent over by Paul Dummett, clearance by Kyle Letheren.81:43
The ball is swung over by Chris Johnston, Lee Mair makes a clearance.81:31
Danny Racchi takes a short corner.81:16
Centre by Rory McKeown, blocked by David Barron.80:01
Sam Parkin is ruled offside. Kyle Letheren takes the free kick.76:18 Substitution
Substitution Chris Johnston is brought on as a substitute for James Dayton.76:18 Substitution
Substitution (Kilmarnock) makes a substitution, with Rory McKenzie coming on for Gary Harkins.75:56
The official flags Danny Racchi offside. David Barron restarts play with the free kick.74:18
Paul McGowan takes a shot. Manuel Pascali gets a block in.74:02
Dougie Imrie crosses the ball, clearance by Liam Kelly.
Gary Teale produces a cross, Kyle Letheren makes a save.71:52
A cross is delivered by Paul McGowan, Lewis Guy takes a shot. Effort on goal by Sam Parkin from just inside the area clears the bar.71:02
Liam Kelly concedes a free kick for a foul on Jim Goodwin. Direct free kick taken by Jim Goodwin.69:06
Free kick awarded for an unfair challenge on Paul McGowan by Manuel Pascali. Strike on goal comes in from Dougie Imrie from the free kick, save by Kyle Letheren.68:48
The ball is crossed by Dougie Imrie, clearance by Cillian Sheridan.68:13
Outswinging corner taken right-footed by Gary Teale from the left by-line, Michael Nelson manages to make a clearance.67:59
Dougie Imrie delivers the ball, clearance by Michael Nelson.66:39
Gary Harkins restarts play with the free kick.66:39 Booking
Booking Caution for Lewis Guy.66:31
Lewis Guy gives away a free kick for an unfair challenge on Gary Harkins.64:39 Substitution
Substitution Dougie Imrie on for Steven Thompson.64:39 Substitution
Substitution Kenny McLean leaves the field to be replaced by David Barron.64:39 Substitution
Substitution David van Zanten leaves the field to be replaced by Sam Parkin.64:08
The ball is delivered by Paul Dummett, Kyle Letheren manages to make a clearance.63:35
Gary Harkins challenges Jim Goodwin unfairly and gives away a free kick. Paul McGowan takes the free kick.62:37
Liam Kelly produces a drilled right-footed shot from 20 yards. Blocked by Lee Mair.62:04
James Fowler concedes a free kick for a foul on Paul McGowan. Lee Mair restarts play with the free kick.60:02 Goal scored
Goal! - James Dayton - Kilmarnock 3 - 0 St Mirren Goal scored by James Dayton from close range to the top right corner of the goal. Kilmarnock 3-0 St Mirren.58:11
Free kick awarded for a foul by Jim Goodwin on Gary Harkins. Free kick crossed right-footed by Michael Nelson, save by Craig Samson.56:40
Danny Racchi sends in a cross,56:21
Assist on the goal came from Danny Racchi.56:21 Goal scored
Goal! - James Fowler - Kilmarnock 2 - 0 St Mirren James Fowler finds the back of the net with a goal from close in to the bottom right corner of the goal. Kilmarnock 2-0 St Mirren.54:32
The ball is swung over by Gary Teale.53:45
Danny Racchi takes a shot. Jim Goodwin gets a block in. Liam Kelly has an effort at goal from outside the penalty box missing to the wide right of the goal.52:49
Gary Teale produces a left-footed shot from outside the box and misses left.51:52
Paul McGowan takes a shot. Kyle Letheren makes a comfortable save.50:50
The ball is delivered by Gary Harkins, save made by Craig Samson.48:59
The referee blows for offside against Steven Thompson. Manuel Pascali takes the indirect free kick.47:05
Foul by Paul McGowan on James Dayton, free kick awarded. Gary Harkins restarts play with the free kick.45:52
Gary Teale produces a right-footed shot from the edge of the area and misses to the left of the goal.45:34
Gary Teale sends in a cross, Manuel Pascali makes a clearance.45:01
The referee gets the second half underway.45:00 +1:01 Half time
Half Time The half-time whistle blows.43:32
Gary Harkins takes the direct free kick. Liam Kelly takes a shot. Comfortable save by Craig Samson.43:32 Booking
Booking Booking for Lee Mair.43:20
Lee Mair challenges Liam Kelly unfairly and gives away a free kick.40:50
Paul McGowan takes a shot. Save made by Kyle Letheren.39:44
Centre by James Dayton, Headed effort from inside the area by Gary Harkins misses to the right of the target.39:25
Paul Dummett sends in a cross, clearance made by James Dayton.38:38
The referee blows for offside. Craig Samson takes the free kick.37:34
Kenny McLean sends in a cross, Michael Nelson manages to make a clearance.36:56
The ball is crossed by Danny Racchi.35:38
The ball is crossed by Lewis Guy.34:20
Free kick awarded for a foul by Jim Goodwin on Gary Harkins. Rory McKeown restarts play with the free kick.34:08
Paul Dummett crosses the ball.33:38
The ball is delivered by Gary Teale, Paul Dummett takes a shot. Blocked by Michael Nelson.32:09
Paul Dummett takes a shot. Ryan O'Leary gets a block in. Gary Teale takes a shot. Save by Kyle Letheren.31:55
Kenny McLean produces a cross, clearance made by Kyle Letheren.28:11
Free kick crossed right-footed by Danny Racchi from left wing, Craig Samson makes a save.28:11 Booking
Booking David van Zanten is cautioned by the ref for unsporting behaviour.27:54
James Dayton fouled by David van Zanten, the ref awards a free kick.25:45
Assist on the goal came from Danny Racchi.25:45 Goal scored
Goal! - Cillian Sheridan - Kilmarnock 1 - 0 St Mirren Cillian Sheridan grabs a headed goal from close in. Kilmarnock 1-0 St Mirren.25:37
The ball is delivered by Danny Racchi,24:42
A cross is delivered by Danny Racchi, clearance made by Jim Goodwin.23:51
Centre by Danny Racchi, save made by Craig Samson.23:34
James Dayton sends in a cross, Paul McGowan manages to make a clearance.22:12
Gary Teale takes a shot. Save by Kyle Letheren.22:03
Paul Dummett sends in a cross, clearance by Michael Nelson.20:45
Unfair challenge on Gary Harkins by Jim Goodwin results in a free kick. Free kick taken by Danny Racchi.14:05
James Dayton takes the free kick.14:05 Booking
Booking Marc McAusland booked.13:59
Lee Mair is penalised for handball and concedes a free kick.13:08
Manuel Pascali gives away a free kick for an unfair challenge on Paul McGowan. Marc McAusland takes the free kick.11:28
Lewis Guy takes a shot. Steven Thompson produces a left-footed shot from just outside the area that goes harmlessly over the bar. Save made by Kyle Letheren.10:27
Effort on goal by Jim Goodwin from outside the box goes harmlessly over the bar.9:01
Corner taken by Gary Teale from the left by-line, Kyle Letheren makes a clearance.8:40
Paul McGowan takes a shot. Save made by Kyle Letheren.7:17
Free kick awarded for a foul by Steven Thompson on Liam Kelly. Ryan O'Leary takes the free kick.5:44
Steven Thompson challenges Ryan O'Leary unfairly and gives away a free kick. Direct free kick taken by James Dayton.5:15
Michael Nelson produces a right-footed shot from the edge of the area and misses to the left of the goal.4:33
Gary Harkins takes a shot. Corner taken by James Dayton played to the near post, Marc McAusland manages to make a clearance. Paul Dummett manages to make a clearance.4:14
The ball is sent over by Kenny McLean, Kyle Letheren makes a save.3:19
Jim Goodwin challenges James Dayton unfairly and gives away a free kick. Direct free kick taken by James Dayton.2:35
James Dayton sends in a cross, save by Craig Samson.1:51
Kenny McLean takes a shot.0:00
The ref blows the whistle to start the match.
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