They ousted Speaker Melvin Neufeld of Ingalls.
The full House still has to ratify O'Neal's selection when the 2009 Legislature convenes on Jan. 12.
Republicans will hold a 77-48 majority, and the minority party traditionally defers to the majority party's choices.
The vote among Republican representatives and representatives-elect was 41 for O'Neal and 36 for Neufeld.
Some Republicans were dissatisfied with Neufeld because of high-profile policy defeats on gambling and energy during the past two years.