Quote from mvalley:
I had many a order cancelled on IB because IB was unable to obtain the market opening price for me.
My understanding is that it is not IB's computer that is canceling the order, it is the computer at the exchange. That is where the decision is ultimately made (unless your limit price is totally out of whack in which case IB will inform you immediately). Also, NASDAQ may not have an official "opening print" but the opening price as determined by NASDAQ's SuperSoes is for all practical purposes an opening print. That is what is reported as the opening price by all historical quotes services and that is the price you get using an OPG order at IB (or it is cancelled if your limit price cannot be filled) just like an NYSE OPG order. So what's the difference?
Can you move the market with a big OPG order? Why not? It is still an auction, it just happens in slow motion. No one can submit orders a few minutes before the open while the exchange figures out a "fair" opening price by matching all the market order with limit orders and if you have a large enough limit order to suck up all the remaining market orders then that is where the opening price will land. Without your (large) order the price would settle on the next limit order in the queue so the market opened at your price instead. So yes, you could theoretically "move the market". I'm no expert in this but that's how I understand it works.