The Scotland international midfielder has been an ever-present for West Brom in recent weeks, starting the club's last six Premier League matches.
Dorrans was rarely used prior to that, but two goals in his last four matches – including a special effort in the club's 3-1 loss at Manchester City on Monday – have showcased his quality.
And experienced defender Olsson believes the 26-year-old can play a key role in West Brom's survival bid.
The Hawthorns outfit sit three points above the relegation zone with four matches to play and Olsson told the club's official website: "He's in great shape and doing very well in his last few games.
"It means a lot to have him in good form. We know he can get a few goals, is good on set-pieces, can get assists and has a good work-rate.
"It is good to have him back to his normal self.
"He has had a tough season but he's done very well in the last few weeks."
West Brom's next clash is a home fixture against the 12th-placed West Ham on Saturday.
Get the best features, fun and footballing frolics straight to your inbox every week.
Thank you for signing up to Four Four Two. You will receive a verification email shortly.
There was a problem. Please refresh the page and try again.