Johnny Russell was the hat-trick hero as United returned to winning ways to boost top six aspirations. The single goal victory in no way adequately reflected United's superiority and only the two conceded goals, and in particular the manner of them, both from corners, took the gloss of a great team display.
For the first match after the break, both teams made three changes. Gary Mackay-Steven returned to the United starting line-up for the first time since the end of November, along with Keith Watson and Mark Millar. John Souttar, Richie Ryan and Stuart Armstrong made way. Jon Daly went back up front with Sean Dillon stepping back from midfield to his more accustomed central defensive beat. For Killie, Danny Racchi, Ross Barbour, Mohamadou Sissoko came in for departed pair Liam Kelly and Michael Nelson as well as the benched Borja Perez.
Unlike Dundee, Rugby Park was a no snow green oasis with the pitch looking in fine fettle for a game vitally important to both sides' top six ambitions, Killie sitting in seventh place, two points ahead of United.
United were first to threaten after four minutes. Gary Mackay-Steven won the first corner of the game. And from his kick, Gavin Gunning's attempted hit was almost a complete fresh air shot. That allowed the home side to break upfield and Dillon had to use his strength to clear the ball from Paul Hefferan.
As the Terrors maintained their attacking momentum they had the ball in the net after six minutes. Barry Douglas delivered a free kick from the left which Daly just failed to make contact with, but Johnny Russell didn't and knocked the ball over the line, only to be flagged offside!
Apart from a lung bursting James Dayton run, play was very much confined to the Killie half.
With 15 minutes gone, GMS showed how delighted he was to be back in action and provided a champagne moment with a sublime piece of skill with both his head and foot to leave two defenders in his wake before being fouled!
So it was all the more frustrating that United went behind three minutes later and not for the first time the source was a set piece. From their first corner taken by Dayton, the United defence failed to clear their lines. And after a Danny Racchi effort was blocked, Manuel Pascali rammed home the rebound from inside the six-yard box.
Two minutes later, Daly met a header from the right, but just couldn't get enough purchase on the ball and it drifted well past.
The Tangerines' dominance wasn't quite so evident, but with John Rankin prominent in breaking up play in midfield, there was no threat at the other end either.
But the midfielder was equally as potent in attack and just after the half hour mark his diagonal ball found Keith Watson whose downward header fell to Daly, but the striker's shot on the turn went wide.
No less than 34 minutes had gone before Rado Cierzniak had a save to make and it was one of no consequence from a half-hit Cillian Sheridan effort that was going past the post.
Two minutes later a GMS shot was deflected for a corner as United again started to dominate. There was a narrow escape for the Ayrshire side after 38 minutes when Daly, at the far post, just failed to make contact with Russell's cross from the right.
But two minutes from the interval, United deservedly levelled.
Watson's deep cross on the run was cleared by Ryan O'Leary under pressure from Daly, but only to Russell who rammed the ball first time low into the net from 12 yards.
On the stroke of half time, Killie almost regained the lead. Sheridan's deep cross from the left was headed past by Heffernan under pressure from Douglas, but it would have been a travesty had he scored.
Half-time: Kilmarnock 1 United 1
Fully six minutes of the second half elapsed before we had anything resembling a chance, a good move by down the right ending with Dayton's full-blooded shot on the turn from the edge of the box going narrowly past.
United's first effort of the second half came from a Douglas corner which Gunning, at full stretch, volleyed over from six yards.
On the hour mark, Rado was tested for the first time when Rory McKeown worked his way into the box and the United keeper did well to beat away his sweetly struck shot.
Three minutes later, we did get a goal and it was United who got it.
Again it came from a Watson cross from the right and again it was Russell who scored directing a downward header past an exposed Cammy Bell.
Midway through the second period, Russell could have sealed victory, but was denied a third by Bell after being sent clear by GMS.
Shortly afterwards Kilmarnock made a double substitution as they tried to rescue the game. A Russell run almost brought a third, but his attempted pass to the unmarked Daly took a fortunate deflection to safety for the home defence.
With 14 minutes left, Killie's Ross Barbour was the first player to be booked for bringing down GMS in full flight. Three minutes later Gunning was on the end of a another Douglas corner, but from an acute angle could only direct his effort straight at Bell.
Having rarely threatened in the second period, Sissoko let fly from fully 35 yards with a first time hit which to the relief of the Arabs behind the goal whistled fractionally wide.
Six minutes from the end Gunning conceded a corner at full stretch from a teasing McKeown cross from the left as the home side upped their efforts in pursuit of the equaliser.
With four minutes left, GMS was replaced by Rudi Skacel and within a minute, it was game set and match when Russell ran on to a long ball from Douglas out of defence to confidently steer the ball into the far corner to complete his hat-trick.
Spoiling an otherwise near perfect afternoon, United conceded a last gasp goal from another corner with Pascali bundling the ball over the line at the front post.
Kilmarnock: Bell, Fowler, O'Leary, Sissoko, McKeown, Dayton , Pascali, Barbour (Winchester 77), Racchi (McKenzie 69), Hefferman, Sheridan (Perez 69).
Subs not used: Letheren, Tesselaar, Hay, O'Hara
United: Cierzniak, Watson, Dillon, Gunning, Douglas, Flood, Millar, Rankin, Mackay-Steven (Skacel 86), Russell (Gardyne 90), Daly.
Subs not used; Banks, Dow, Barrett, Petrie, Souttar.
Referee: Craig Thomson
Crowd: 4,112