Getting ThereFrom the Lake O'Hara campground, cross the road and find a well-travelled trail. Cross Cataract Creek on a wooden footbridge and walk the trail upstream for 200m or so until you spy an avalanche gully leading upslope (there was a small cairn here, and the climber's trail is obvious at this spot. Follow the trail (or your nose) up the hill through the trees (also some flagging at the time of our ascent). Work left at some cliffs until you find a way through them, then follow ledges and ramps back right to the base of the route. A lone tree (the highest one) at the base of a large chimney marks the start of the route.
Descent: Work your way to the obvious col east of the ridge. This is 4th class, and in dry conditions, we were able to downclimb. However, many rap stations suggest that this may not be possible for some parties.
Once at the col (DO NOT DESCEND IT!), contour around the S side of S. Wiwaxy tower on ledges (and a climber's trail). Another gully below will tempt you, but stay high and head for another notch to your left (as you are descending; cairn). From this notch, you can see down the proper descent gully and right into Lake O'Hara. Descend loose scree and sand for several hundred meters and catch the Wiwaxy Gap trail back to Lake O'Hara.
External LinksWe found the most popular guidebook (which will remain unnamed) to be filled with much useless (read: incorrect) beta.
However, there is a solution. I don't know the folks that put this CD together (really), but it was invaluable in Canada. Have a look and see for yourself. This CD has a detailed, pitch-by-pitch topo of the Grassi Ridge and many other Canadian Rockies classics.