Bobby spring a surprise by not naming the same eleven that had lost to Dundee United last Sunday, Paco Luna taking the place of veteran Craig Brewster.
Killie started in determind fashion, and Tony Caig needed two attempts to collect the ball after a dangerous cross from Greg Shields. Paul Hilland, in only his second senior match, stopped a good goalscoring opportunity falling to Andy McLaren when he produced a magnificant challenge just as the former Reading star was about to shoot.
On eight minutes Hibs had the woodwork to thank for still being on level terms. Killie won a corner which was swung in by Murray. Tony Caig couldn't get to the ball, it was met by striker Craig Dargo, whose vicious volley smashed off the upright.
Hibs then passed up a great opportunity to score when Garry O'Connor was sent clear by Freddy Arpinon, but the 18 year old couldn't took too much time in shooting, and the ball was cleared by Peter Canero.
The home side then took a deserved lead on 17 minutes. Andy McLaren raced down the wing and crossed for Ngonge, who fired the ball past the despairing Caig.
Just before half time Kilmarnock nearly doubled their lead, but Craig Dargo just missed a cross by Ally Mitchell.
Hibs started the second half looking like they meant business and finally forced home 'keeper Gordon Marshall into action. Captian John O'Neil crossing for Paco Luna, but the Spaniard's shot was beaten away by Marshall.
Hibs huffed and puffed but never really troubled the Kilie No 1, O'Connor forcing Marshall to block an angled drive, but it clearly wasn't going to be a happy return for Williamson.
Michel Ngonge looked to have put the game beyond doubt when he lobbed Caig, but the referee ruled that the former Watford striker was offside.
Garry O'Connor tried in vain to get Hibs back on level terms, with Scotland boss Berti Vogts watching, but he was twice thwarted by Marshall.
Overall, quite a poor performance. Bobby Williamson may well freshen things up for the next two matches, both at Easter Road.