In addition to dragging and dropping views in the Workbench the order of views can also be rearranged within a tabbed view stack.
Choose Window > Perspective > Reset Perspective to reset the Resource perspective back to its original layout.
Click on the Outline title bar and drag it on top of one of the navigation views. The Outline will now be stacked on top of one of the navigation views.
Click the tab of the Project Explorer view and drag it to the left of the Outline tab.
Once the cursor is to the left of the Outline tab and the drop outline is shown, release the mouse button.
Observe the Project Explorer tab is now to the left of the Outline tab.