© PA Photos
The hosts started the better of the two teams and stand-in goalkeeper Boaz Myhill was called into action early to keep out Ben Watson's powerful strike from the edge of the area.
Wigan continued to control possession throughout the half but the visitors were unlucky to not open the scoring when a counter-attack was ended by Ali Al-Habsi's clearance on the edge of the area.
Al-Habsi came to the rescue once again midway through the first half as he blocked Morrison's effort before saving at the feet of Romelu Lukaku.
However, Al-Habsi had little chance to keep out West Brom's opener, with Morrison being left with the simple task of heading past the goalkeeper following a cross from Chris Brunt.