When was God's plan determined before creation?

Les explains that it was all foreknown before anything was ever created, and it was consummated, you might say, in the thought process of the Trinity. He clarifies that he does not imply the three persons sat down around a table and debated what would happen as men might do. But within the Trinity of the Godhead, whether it was a split second or whatever, nevertheless all three persons of the Godhead had agreed that this was the way they would do it. This is what the determinate counsel means—the coming together and thinking all of this through by the Godhead, the three persons of the Trinity, and they all agreed that this was the only way that they could make it all come to pass.