Kris Boyd grabbed a double to give Kilmarnock a convincing victory that dumped Livingston back to the bottom of the Scottish Premier League.
The striker fired home from close range after defender Harald Pinxten failed to clear a cross from Garry Hay.
Allan Johnston set up Steven Naismith to stroke home the second.
Livi failed to create many chances and Boyd chipped in his 14th goal of the season and his sixth in his last four games to secure victory for Killie.
It moves the Ayrshire side level on points with fourth-top Rangers, for 24 hours at least.
Striker Robert Snodgrass had returned to the Livi starting line-up, with Ramon Pereira dropping out, as they looked for a third successive win.
Colin Nish started for Killie after Rhian Dodds failed to recover from a knock and he combined well with Boyd up front.
Boyd, likely to be included in the Scotland Future squad, was denied early on by an outstanding one-handed save to tip the ball over.
Killie had to scramble the ball clear after goalkeeper Alan Combe dropped a cross and Jason Dair sent shot over the crossbar, but the visitors deserved to take the lead after 26 minutes.
Hay's cross from the left should have been cleared by Pinxten, but the ball stuck under his foot and broke to Boyd, who finished clinically from seven yards.
Killie hit a second three minutes later after a fine sweeping move.
Johnston's through-ball was dummied by Nish and Naismith continued his run from deep to stroke the ball past Roy from 12 yards.
Pinxten looked set to atone for his earlier error, but Killie defender Simon Ford beat him to Tierney's free-kick to divert the ball over for a corner.
Livi needed a good start to the second half and Paul Dalglish tried his luck from 30 yards, but Combe was behind the effort, despite the ball looping up off his chest.
Boyd fired into the side-netting and had a 15-yard shot deflect off Greg Strong and dribble wide to the relief of a wrong-footed Roy.
Roy got in an awful tangle from a vicious inswinging corner from Hay, but Nish could only divert the loose ball over the bar.
Livi were struggling to create, although skipper Dave MacKay sent a header just wide in the 70th minute.
But the match was ended as a contest seven minutes from time when Hay's hooked ball caused havoc in the Livi rearguard and Boyd kept his composure to coolly lift the ball over the onrushing Roy.
Livingston: Roy, Mackay, Pinxten, Strong, Tierney, Brittain, Walker (McPake 72), Neil Barrett, Dair (Vincze 63), Dalglish, Snodgrass (Pereira 54).
Subs Not Used: Dorado, Miller, Scott, McKenzie.
Booked: Neil Barrett.
Kilmarnock: Combe, Greer, Ford, Wright, Fowler, Invincibile (Murray 84), Nish (McDonald 84), Johnston, Hay, Naismith (Wales 84), Boyd.
Subs Not Used: Smith, Lilley, Campbell, Pronevych.
Goals: Boyd 26, Naismith 29, Boyd 82.
Ref: E Smith