With just six minutes on the clock, the Baggies boss stepped out of his technical area and stopped a loose ball from going out of play.
The 40-year-old clearly thought that Sekou Mara's through ball for Adam Armstrong had went off the pitch.
He duly stuck out his left leg to divert the ball to Darnell Furlong, but referee Sam Allison wasted no time in brandishing the red card.
Corberan protested his innocence to the match official, but it was to no avail as he was sent to the stands following his moment of madness.
Speaking on commentary for talkSPORT 2, ex-West Ham striker Dean Ashton said: "What a strange circumstance.
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"The ball looks like it's going to go out, but then it just curls, stays in and bounces across the line."
The game then restarted with a drop ball, with Corberan's dismissal one of the most bizarre red cards this season.
Things quickly went from bad to worse when Ryan Fraser broke the deadlock for the Saints in the 14th minute at The Hawthorns.
And David Brooks then wrapped up the victory in the 73rd minute as the Saints leapfrogged Leeds into second spot in the Champions League.
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As per FA rules, Corberan will not be allowed to take part in an immediate post-match interview to give his say on the matter.
And with the club's prospective new owner in attendance, it was the worst possible start for the hosts.
Speaking to Sky Sports ahead of the match, Corberan declared he was 'fully focused' with Shilen Patel edging closer to a complete takeover.
He said: "It is a positive thing for the club. We are very pleased and looking forward to starting a new moment for the club.
"But in a very demanding period, I am fully focused to prepare for the game because we are playing many games in a row."
Patel's takeover is reported to be worth £60million and it will bring an end to Guochuan Lai's unsettled reign in the Midlands.
Lai, who bought the club for over £200m in 2016, had been under pressure to sell the club amid failure to pay back loans.
West Brom have been seeking a new buyer amid increasing losses of money, with more than £20million said to be borrowed from MSD Holdings Limited.