Costco for meats, dairy, and bakery, hands down. To avoid the lines try shopping late afternoon (~3-4pm), and avoid Saturdays completely! I have not been myself, but my parents have said that the Okotoks Costco is way less busy, including Saturdays.
I get the rest of my groceries at Sobeys as I only like to buy 1 or 2 days worth of produce at a time and it's really close to my house. The prices at Sobey's are pretty fair.
Edit: Oh ya, when you go to Costco, buy these! Freakin' yum!