At what point does the reversal occur?
I would say that the reversal of Oedipus' fate as well as the reversal in the tragedy comes out in Act IV. The revelation that emerges from Act IV can be seen in the Chorus' reaction to Oedipus. From a point of view where he was seen as an exalted ruler that was capable of giving guidance to a people in need, he becomes viewed as one who is pathetic, wretched in his own condition. It is a massive reversal that literally shifts everything. It is one in which Oedipus has become a source of pity as opposed to a source of respect. It is one in which the reversal is understood by both the external audience and characters. Yet, it is also understood by Oedipus himself, as he recognizes fully that his own condition has becomes one that has exposed everything about him. There is a nakedness that is evident in Oedipus, for when the revelation becomes fact and the Chorus bemoans what has happened, Oedipus is left with no place to go, no refuge that can be taken. The terror that awaits him in Act IV with his mother/ wife taking her own life along with his own blinding and self- exile is rooted in the moment of reversal that is so painfully evident in Act IV.