Albion suffered only their second away League defeat of the season at Roots Hall last night.
Defender Nathan Jones gave Southend the points with his first senior goal three minutes from time.
He slammed in the rebound when Neil Tolson headed against the post from Mark Tinkler's cross. It rewarded a storming second half performance from the home side after Paul Watson had fired the Seagulls into a 23rd-minute lead from 30 yards.
Martin Carruthers equalised on 55 minutes and Jones' late winner sentenced Albion to their seventh successive defeat in visits to the Essex seasiders.
Oatway recovered from an ankle injury sustained in Saturday's F.A. Cup draw at Peterborough to take his place in an unchanged Albion line-up.
The only alteration was on the bench, young striker Ramsay replacing goalkeeper Ormerod.
Southend were forced into a change for the first time in nine matches, Morley coming in for the suspended Roget.
Booty was passed fit, despite suffering a neck injury in United's unfortunate F.A. Cup exit at Torquay.
Carr, making only his third appearance for the Seagulls, was cautioned inside the opening minute for a foul on Southend's topscorer Tolson.
It added to the former Gillingham stopper's booking on his debut at Cheltenham last month.
Neither keeper came remotely close to being tested in a desperately dull opening.
A long range shot by Booty for Southend, which went well wide, and a free-kick from Aspinall which was blocked was all that both teams could muster.
Houghton had a chance to give Southend a 21st minute lead, but he dragged his effort wide from a central position just outside the Albion area.
Albion were enjoying plenty of possession without posing a threat. That all changed though on 23 minutes with a spectacular goal by Watson.
The Hastings-born defender collected Oatway's clever back heel 30 yards out and curled a delightful left foot shot over Capelton.
Watson's first away goal for the club followed one on his full home debut against Hull in August. It was every bit as good as Andy Clarke's unstoppable drive from similar distance for Peterborough against Albion three days earlier.
Boosted by the breakthrough, the Seagulls started to take charge. A dangerous move ended with Aspinall using his hand to control Rogers' intelligent knockdown from Freeman's deep centre.
Tolson rushed off the pitch with blood seeping from a head wound after a challenge by Carr. Referee Jordan clearly felt nothing untoward had happened as he re-started the game with a drop ball.
Southend played with 10 men for nine minutes before former York forward Tolson returned to the fray.
Oatway had already clashed with Tinkler when he was involved in another incident with Beard, which cost the tigerish midfielder a 41st-minute caution.
Tolson followed Oatway into the book just before the break for a foul on McPherson.
The Southend striker was on dodgy ground seconds later when he was lectured by the ref, along with Cullip.
Carr and Tolson were having quite a battle. The Albion defender needed treatment early in the second half when the Southend striker, who had stitches in a cut above his right eyebrow while he was off the pitch, caught him in the face with his boot.
Freeman, playing his last game before a 3-match ban, was the next casualty. He also needed attention from physio Malcolm Stuart following a knock on his right knee.
Walton was called into serious action for the first time in the 53rd minute to claw away a cross by Connelly when the Scottish winger got the better of Campbell down Albion's left flank.
Southend levelled in fortunate fashion 10 minutes into the second half.
Connelly cut in from the right wing to strike a shot which was going well wide when it struck team-mate Tolson.
The deflection wrong-footed Walton and his defence, and they looked in vain for offside as Carruthers slotted his sixth of the season into a gaping goal.
The Seagulls had looked comfortable throughout the first half, but it was suddenly an entirely different game. Beard spurned a great chance to put Southend ahead on 59 minutes, blazing over the bar when another deflection put him clean through.
Connelly, non-existent in the opening 45 minutes, was beginning to see a lot of the ball. He cut inside Campbell again before unleashing a drive which Walton did well to hold, moving to his left.
Converted for the new archive on 30 June 2000. Some images and formatting may have been lost in the conversion.
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