EDMOND, Okla. – Today marks the beginning of “official” play for the U.S. Senior Open Golf Tournament at Oak Tree National in Edmond, Okla.

The United States Golf Association released groupings and tee times for the first two rounds of the U.S. Senior Open.

Two groupings stick out more than any others, and they`ll be playing back-to-back during the first two rounds.

One group features a trio of previous winners at Oak Tree.

It includes Jeff Sluman, winner of the 1988 PGA Championship at Oak Tree, with Jay Haas, winner of the 2006 Senior PGA Championship at Oak Tree, with Scott Verplank, who won the 1984 U.S. Amateur at Oak Tree, and who will be making his first appearance on the Champions Tour after turning 50 on Wednesday.

They will tee off at 1:52 on Thursday afternoon.

The next group following them is an all-Oak Tree gang trio.

Willie Wood, Bob Tway, and Gil Morgan will all play together in that group, teeing off at 2:03 on Thursday.

Those two groups will tee off at 8:07 am and 8:18 am on Friday, respectively.

Reigning U.S. Senior Open champion Kenny Perry will tee off in the group before those two, at 1:42 Thursday and 7:57 am Friday.