[Brian]

OmniFocus treats actions within a project as an ordered list of actions. You can get a sorted list of actions for a particular project in context view, though.

Select one or more projects in Planning view sidebar.
Select View -> Focus on selected projects
Switch to context view, sort by due date. (Or start date)

If this is something you'll use frequently, you can select "Save this view as new perspective" from the perspectives menu.