O'Brien was knocked out by the New Zealander in an off-the-ball incident in Saints' 26-6 Super League victory over the Dragons in Perpignan last Saturday.
Taia pleaded not guilty to a charge of reckless striking with the shoulder at a Rugby Football League disciplinary tribunal but was found guilty of the grade C offence by the panel.
Taia was also fined £300 by the RFL and will now miss the Dragons' upcoming games against Bradford, Wigan and Leeds.
A statement from the RFL read: "Catalan Dragons player Zeb Taia has been suspended for three games after an RFL disciplinary tribunal found him guilty of committing a Grade C reckless striking with the shoulder offence on Gareth O'Brien of St Helens."
Saints coach Nathan Brown was furious after the incident, which occurred in the build-up to Saints' second try and came less than a fortnight after O'Brien was hurt in a similar challenge from Wigan's Scott Taylor.
Brown branded the Taia challenge as "disgraceful" and "appalling" after the game and has now confirmed O'Brien, who is on loan from Warrington, will miss this weekend's home clash with London Broncos.
Brown said: "He won't play. He is going to see a specialist.
"I believe he'd pass the tests you're supposed to do but he's had two heavy knocks in two weeks now and I don't believe it's right to play him.
"The doc's going to send him to see the right people and we'll see what they say."
St Helens prop Louie McCarthy-Scarsbrook and Catalan's Mikael Simon avoided suspension after submitting 'early guilty pleas' to grade A charges of punching after an altercation in the same game.
Hull KR's Lincoln Withers was suspended for one match after submitting an 'early guilty plea' to a grade B charge of dangerous contact following a challenge on Wigan full-back Ryan Hampshire.
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