Tab Order in interface builder?

The Cocoa term you're looking for is "key view loop". Use the initialFirstResponder and nextKeyView outlets to connect the views together in the order you'd like to tab through them.

This is mentioned in the documentation here.

Note that the items which can receive keyboard focus will change depending on the Full Keyboard Access setting (in System Preferences > Keyboard); if disabled, tabbing will skip over various items in your key view loop.

Let the outlets are named as a, b and c. Mac default tab order is a -> b -> c -> a

But Your desired tab order is a -> c -> b ->a :

Using IB:

Set a as the initialFirstResponder.

Then put the nextKeyView accordingly as a to c, c to b and c to a.

But I prefer using codes, here it become easier to add more. As in complex UI there may be 30+ controls and you might require to shuffle and even insert new control!!!

So you can achieve the same as :

[self.a setNextKeyView:self.c];
[self.c setNextKeyView:self.b];
[self.b setNextKeyView:self.a];