If you are looking for the best quality food, then Wholefoods Market on Sunset Drive wins hands down (in Bishop Ranch). Otherwise, the new SafeWay at Gale Ranch Plaza should meet most of your needs. Also, don't miss Trader Joe's in Danville for good quality low-priced groceries etc.
If you are looking for good produce then the farmers' markets in Danville or San Ramon are favorite.
Some may say the new Draegers store at Blackhawk is worth a look but in my view it is just the same products you can get elsewhere but Draegers charge you more.