For the second time in this year's tournament, Kilmarnock needed extra time to overcome First Division opponents in the CIS Insurance Cup.
Kilmarnock were made to work hard by Livingston
Defender Frazer Wright's powerful free-kick five minutes before the end of added on time settled the match.
Gary Wales showed his shot-shy Killie team-mates the way to goal with a great strike in the 57th minute.
But the First Division leaders fought back and Steven Craig's 72nd-minute penalty forced another 30 minutes.
Kilmarnock had the majority possession after a slow start but failed to capitalise - and the First Division leaders looked dangerous when they broke forward.
Livi right-back Jason Thomson came close in the fourth minute with a first-time shot which curled narrowly wide of the target.
James Fowler shot wide from long-range and Danny Invincibile failed to worry the Livi defence with his header as Killie pressed. Invincibile came closer on the half-hour mark as he headed wide at the back post after a brilliant run and cross from left-back Garry Hay.
The hosts' dominance was growing and Wales was inches away from the top corner with a 25-yard free-kick, before Steven Naismith's volley on the turn from 16 yards was held by goalkeeper Craig Wight.
Livi almost snatched the lead 90 seconds before the break when Steven Tweed's header landed on the roof of the net.
Wales put Killie ahead when he worked a shooting chance on the edge of the box and struck a fierce effort low into the corner.
Livi substitute Paul Shields laid the ball off for Thomson to strike a 25-yard effort which Graeme Smith palmed over.
Soon after, the visitors won a penalty when Grant Murray pulled back David Mackay and Craig lashed the 72nd-minute spot-kick into the top corner.
Killie were stung into action and Allan Johnston saw a shot tipped on to the bar by Wight.
Both sides had chances for a late winner but teh best fell to Livi's Steven Weir, who hammered a volley just over from a tight angle.
Livi started well in extra-time but Weir could not direct Shields' powerful drive on target.
Killie regained the territorial advantage for the rest of the first period but the chances dried up as both sides tired.
The game looked to be heading for penalties but Killie won a free-kick 20 yards out and Wright blasted a low strike through the wall to win the contest.
Kilmarnock: Smith, Greer (Locke 80), Hay, Frazer Wright, Grant Murray, Fowler, Johnston, Invincibile (Stephen Murray 75), Naismith, Wales (Nish 80), Fernandez. Subs Not Used: Harpur, Di Giacomo.
Booked: Locke, Fernandez. Goals: Wales 57, Frazer Wright 115.
Livingston: Craig Wight, Thompson, Mackay, McPake, Tweed, Mitchell, Hamill (Shields 61), Walker (Smylie 61), Dorrans (Weir 83), Makel, Craig. Subs Not Used: Stewart, Fox.
Booked: Mackay, McPake, Makel. Goal: Craig 72 pen.
Ref: E Smith