Tuesday is D-Day for UBS AG, when Chief Executive Oswald Grübel gives the first peek at how he plans to turn around the struggling Swiss banking giant.

Since taking over in February, Mr. Grübel has quietly started a head-to-toe restructuring of UBS, one of the banks hardest hit amid the global downturn. Tuesday, he will lead a full-day presentation in Zurich of his plans to turn around the group.