So, late lunch or snack.
But, at Disneyland/California Adventure i leave the park for Downtown Disney around 1 or so and go to one of the many restaurants there. I personally have been disappointed with the restaurants in both of the parks. The food in Downtown Disney is cheaper and the quality is better.
If visiting a thrill park, I generally just snack on hard-to-mess-up-items (like pretzels) until dinner, then I leave the park, eat a good, sit down meal, and return for a few night time coaster rides.
All you have to do is eat a big breakfast and eat a big dinner (probaly a buffet my style). These will save you time in lunch lines and ride times so you can have fun with your family, friends or who ever is with you