Joao Pedro kept ice cool to secure Albion an historic European point in a feverish atmosphere at the Stade Velodrome in Marseille last night.
The Brazilian forward passed the supreme test of his technique and composure on the hot spot as he guided home an 89th-minute penalty.
His finish, following a foul on the spring-heeled Tariq Lamptey, earned the Seagulls a 2-2 draw which did not look likely when they were caught in the headlights in the first quarter of this Group B contest.
Instead they have a morale-boosting point, have denied Marseille two and are still on the tails of AEK Athens and Ajax, who shared a 1-1 draw in the other game.
Albion now look forward to home and away fixtures with Ajax on October 26 and November 9.
Lamptey, replacing injured Pervis Estupinan at left-back, had a huge part in both goals.
He produced some strong and nimble work to help Kaoru Mitoma set up the lifeline strike put away by fit-again Pascal Gross nine minutes into the second half.
The Seagulls had been left reeling after two goals in the space of about minute just before the midway point of the first half.
Chancel Mbemba and Jordan Veretout, the second after a nightmare miskick by Lewis Dunk, had OM in charge.
But Dunk saved a goal with a superb block in the second half and was a proud skipper as he led his side to a noisy away corner at full-time.
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here