A 4-2 defeat left his side with a record of two wins in 20 games, while the Baggies secured a fourth successive Premier League victory to lift them to third.
And, with his own team hovering three points above the drop zone, O'Neill said: "I think there's a lot to take out of the match, a lot to take out of it.
"We have been beaten, but we look as if we can maybe get a goal again now, which is very encouraging.
"We have a big game on Tuesday night against QPR and we will try to get ourselves prepared for that."
Sunderland trailed to a Zoltan Gera strike, but they were left with a mountain to climb after keeper Simon Mignolet fumbled Chris Brunt's harmless through-ball to hand Shane Long a second goal.
O'Neill added: "Simon has been fantastic for us, absolutely fantastic. He is entitled to something like that now and again.
"It's absolutely and utterly out of character. It just slipped out. He has been terrific for us."