Originally posted by Ollie
Square as in aspect ratio one or square as in rectangular?
Both aerodynamic washout and geometric washout can prevent tip stall in a tapered wing if the right amount of washout is used. Even a tapered and highly sweptback wing can avoid tip stall if enough washout is used. Sight down the wing of any modern jet transport for an eyefull of washout. The designer didn't put it there because HE was twisted. 
The picture I had in my mind was a perfectly flat/rectangular shaped wing, but in hindsight, that was way too general a reference to this situation.
The A-10 wing is a fairly rectangular wing, with the tip chord being shorter than the root, this was the basis of my example. I know of know military or widebody aircraft that stalls the innerwing before the tip, that is a very dangerous situation.