Good bakery in Whistler?
If you don't mind picking the bread up on your way to Whistler (or driving back down) Sunflower Bakery in Squamish is excellent. Some of their bread is available in Whistler at the grocery stores too. In Whistler there's Hot Buns Bakery but I can't remember if they really have much in the way of bread. Gone Bakery behind Armchair Books is good too, but I have no idea if you can buy larger quantities of baked goods from them.
Some of the breads from Terra and Pane E Formaggio in Vancouver are also sold up in Whistler. Beyond that there's good selections of breads and rolls in general at Nesters and IGA.
Pane E Formaggio
4532 10th Ave W, Vancouver, BC V6R2J1, CA