The Carnation Cafe or The Jolly Holiday has cinnamon rolls, yogurt I think, coffee, croissonts,muffins etc to get a quick bite of something that can be eaten in line or while walking.
You can also bring your own breakfast bars or trail mix.
Just last week (sigh!) we had a surprisingly good and VERY quick breakfast at Tomorrowland Terrace. I had a very tasty breakfast burrito, DS had french toast, and DH had a large fruit platter. We hit the park at rope drop, did a few attractions, stopped for breakfast and then went on with our day -- worked great!
I often see people eating breakfast in Downtown Disney right outside where security is I think it is a bakery there. I don't know about quick because there is always a long line but I've heard it is good and cheap.
Im surprised nobody has mentioned PWC at CA...they make the bomb croissant sandwiches and breakfast bowls![]()