Callaghan Valley, Gin Peak and Journeyman lodge
The Callaghan Valley provides a few excellent backcountry options just 30 minutes south of Whistler. It generally stays colder than whistler and gets about 50% more snow!
The most basic is Gin Peak and hanging lake where you can do short day tours straight from the Whistler olympic village or venture further up Rainbow peak. At the time of writing there is a $15 day fee per car and the gates do have limited time window. Visit here for more info: https://www.whistlersportlegacies.com/whistler-olympic-park/overview
The approach is usually following a luge track where it often splits to head up and right toward Gin, or cut left and hit the exit from haging lake. Lots of good options exist from Mellow alpine skiing to steeper tree runs.
Journeyman Lodge and the Callaghan Lake Shuttle.
The other main option is Callaghan Country. This is another XC ski operation which provides a Cat shuttle to Callaghan lake on the weekend as well as an alpine hut with excellent backcountry right out the door. The hut is fully catered and a great place to book a room and meet some new friends. The Journeyman shoulder is the most obvious skiing from the hut, but during good high pressure systems there are endless alpine peaks to ski. On storm days there is some excellent sheltered tree skiing on the other side of Conflict Lake. We recommend trying to schedule a trip with a Cat shuttle to save yourself the massive approach, then camp out or stay in the lodge! See the beta here for more information. Aside from Journeyman shoulder. My favorite zone is T33 with some Couloirs, steep faces, and lots of pillow options. http://callaghantrails.ca/TouringAreas/