If you are in Beijing I find the typical "foreign" bake shops (Paris Baguette, etc) pretty good for some types of bread and croissants. Their products vary so its worth looking around and finding one that has what you are looking for.... I typically go for a rye bread or sour dough and croissants.

As for breakfast foods I find the Beijing supermarket chain Chaoshifa (超市发超市) actually has pretty good selection of western breakfast stuff at some locations (jams/some bread/bacon/cereal/milk/etc).