Dietmar Hamann fluffed a clearance just outside the area and Ormerod calmly dribbled towards Chris Kirkland and drilled it home.
But the hungry Liverpool side looked unshaken by the early setback and created many clear chances in the opening 20 minutes.
Young newcomer Jon Otsemobor was particularly impressive making several good runs down the right flank. His thunderous runs served the home side well as he danced past Rory Delap and whipped in a curling cross, but Emile Heskey was unable to capitalise.
Liverpool continued to pile on the pressure and contained the visitors in their own half, however, the closest the Merseysiders came to scoring in the first half was when Vladimir Smicer had a penalty plea waved away after pushing the ball through two defenders and into the box, but he lost his footing.
Liverpool came out in the second half knowing they had much to do to salvage the game and created some good opportunities.
But it was Liverpool's lacklustre defence who were caught napping again in the 65th minute. James Beattie won a corner off Igor Biscan and Ormerod's weighted kick found Michael Svensson alone in a gaping hole and his powerful header gave Southampton a two-goal buffer.
However, Liverpool maintained their pressure and were rewarded in the 75th minute.
Florent Sinama Pongolle hit a left-footed cross which was blocked, but it fell directly at Steve Gerrard's feet.
The Liverpool captain fired a shot which Southampton goalie Antti Niemi couldn't handle and Heskey was in the right place to finish off and grab a consolation goal.