65 mins
However, Kilmarnock were without their top scorer Colin Nish, who sealed a move to Hibernian on Thursday.
Killie had an opportunity to put Celtic under pressure early on when Willie Gibson's corner broke to Garry Hay but his shot lacked power and was easily cleared. Then it was one-way traffic in the other direction.
Aiden McGeady was the first to try his luck with a 25-yard drive which went well wide of the target.
Scott Brown then embarked on a surging run down the right flank before delivering to the feet of Vennegoor of Hesselink. The striker stumbled over the ball and recovered to have another go but the effort was blocked by Combe.
Celtic cranked up the pressure and McDonald forced a superb point-blank save from Combe, but the Killie goalkeeper was powerless to prevent the striker from opening the scoring seconds later.
Caddis collected Shunsuke Nakamura's pass on the right wing and whipped in a low cross to McDonald, who rifled home from close range with 22 minutes on the clock.
Vennegoor of Hesselink then saw his header crash off the inside of the post before McDonald was twice thwarted in his attempts to net from the rebound, with Frazer Wright and Combe both proving stubborn obstacles.
The home side rallied before the break and Martyn Corrigan saw his smart shot saved by Artur Boruc before Gibson fired wide as Celtic protected their slim advantage at half-time.
Then came a flurry of goals. Celtic claimed their second of the day just seven minutes after the restart when Nakamura's corner was flicked on by Massimo Donati and Caldwell connected powerfully to leave the net bulging with a header from a few yards out.
Vennegoor of Hesselink then helped himself to a goal six minutes later.
McGeady's
pass split the Killie defence and found the Dutchman
unmarked and with plenty of time to pick his spot
and he duly fired a well-struck shot beyond Combe's
reach.
Kilmarnock gave themselves hope of a comeback when Jamie Hamill (right) nodded home from Danny Invincibile's cross after 65 minutes but the joy was short-lived when McDonald pounced on Vennegoor of Hesselink's lay-off to bury a firm shot from 12 yards just a minute later.
With the tie over as a contest, the Celtic fans lustily chanted the name of Samaras and Strachan obliged by throwing the on-loan Manchester City striker into the action for the remaining 20 minutes.
He replaced McDonald and instantly endeared himself to the supporters behind both goals by marking his debut with a goal.
The Greek frontman used his strength to hold off Simon Ford on the right flank before darting infield and tucking a neat left-footed shot past Combe with six minutes to go, to round off a perfect day for the holders.
Sandy's Match Pic's are HERE
