Prior to their respective arrivals in the January transfer window West Brom struggled badly for goals, an ailment that has at least been partially remedied of late.
Fortune, on-loan for the remainder of the season from Nancy, has quickly adapted to English football having scored three goals in four games.
Simpson, who has agreed a similar loan stint, has also impressed with a series of promising displays.
Big impact"Fortune and Simpson have made a big impact. Without those two, we didn't score many goals and if you can't score, you can't win," admitted Mowbray.
"The number of chances early season we didn't convert seemed to happen every week and yet Simpson and Fortune can both score goals and pose problems.
"I've got no problems now with the attacking side of our game. Generally I think we have sorted that side of our game out with the signings we have made."
Defensive mistakesMowbray's chief concern now is to tighten up his injury-hit defence after a mistake-riddled performance in the 3-2 home defeat against Newcastle at the weekend.
The likes of Abdoulaye Meite, Jonas Olsson, Ryan Donk, Leon Barnett and Neil Clement have all been on the sidelines.
Mowbray said: "The attacking side of the team is healthier now and let's hope in the next couple of weeks that we can get the back four back fit and up to speed and doing their jobs.
"When both of those two departments start to function, you have obviously got a better chance and will win some games."