Mapquest
Google Maps
(Please Note: Google Maps inaccurately identifies the green arrow as Madill, OK when in fact it is the University of Oklahoma Biological Station)

The University of Oklahoma Biological Station is located east off Highway 377/99 on Oklahoma University Road.

From Norman:

pdf file with hand drawn map and details

Take I-35 south to Exit 29 in Ardmore.
Head east on Highway 70 out of Ardmore and into Madill.
From Madill, go south on Highway 377/99
Turn east on Oklahoma Unversity Road

From Dallas-Fort Worth:
Take 114 or 121 out of Dallas-Fort Worth
Take I-35 north to Gainesville
Go east on Highway 82 to Whitesboro
Take Highway 377 north to Oklahoma
Turn east onto Oklahoma University Road after crossing the bridge into Oklahoma

From Dallas-Forth Worth - PDF