Scotland midfielder Morrison was forced to miss the Baggies' win over Southampton on Monday night, due to a hamstring problem, but he returned to help inspire Steve Clarke's men to three points which keeps them firmly rooted in the league's top six.
Morrison met a cross from Chris Brunt to head an unstoppable opener past Ali Al Habsi, before a Gary Caldwell own goal put the Baggies in command. Arouna Kone reduced the deficit and the Latics piled on the pressure but could not claim a point.
Maynor Figueroa drilled a low long-range shot just wide for the home side in the fifth minute and James McCarthy's persistence also fashioned an early chance after he robbed Claudio Yacob and pressed forward.
And it took Baggies goalkeeper Boaz Myhill - in for his first senior Baggies game in 21 months due to injury to Ben Foster - nine minutes to prove worthy of his call-up as he pulled off a superb save to deny Ben Watson.
The Baggies went ahead after 30 minutes as Brunt flung in a precise cross from wide on the left and Morrison aimed his magnificent header past Al Habsi from the edge of the six-yard box.
And the visitors almost increased their lead seven minutes later when Billy Jones cut in from the right and unleashed a fierce left-footed drive which flashed just wide of the busy Al Habsi's left-hand post.
That seemingly inevitable second goal duly arrived after 43 minutes when Jones' effort from a tight angle was deflected into his own net by Wigan captain Caldwell - but less than a minute later Kone pulled one back when he poked home Jean Beausejour's cross.
The Baggies should have extended their lead in the 56th minute when Romelu Lukaku lashed a shot on the turn which was brilliantly tipped over the bar by Al Habsi at point-blank range.