I'd like to get the open prices because that's what I backtest on. Last night, using IB's paper trading account, I placed several orders with TIF=OPG, Type=MKT. This morning, they were all executed about 5 minutes before the open and I did not get the published open prices. For example, XOM's open today is 68.47. The price I got was 68.54. Is there any way that I can get the open price guaranteed?