The Ibrox trialist netted both before the break at Almondvale with Ian Black and David Templeton adding further goals in the second half.
Rangers took the lead with a swift move in the 26th minute, as the ball found its way to Lee Wallace whose cross from the left was clipped home by Law at the far post.
Lee McCulloch missed a decent chance a few minutes later when he headed wide from 12 yards, with Law adding a second goal three minutes before the break thanks to a fine individual effort.
The former Motherwell player collected the ball close to the left touchline before racing into the box and finding the top right-hand corner of the net from 16 yards.
The third arrived 20 minutes from time when McCulloch fed Ian Black whose strong run took him into the Albion box, with the midfielder finding the back of the net with a fierce low strike from 18 yards.
And as the Gers continued to dominate with ease, another powerful attack ended with David Templeton firing home the fourth from 22 yards on 74.
Robbie Crawford hit the bar from close range as the visitors chased a fifth, leaving Albion with little more to do than limit the damage.