OPTA is organized into two chapters. Each of the chapters functions independently of each other to operate their programs and activities. The chapters come together under the board for state-wide programs and planning.
Draws membership from Clatsop, Columbia, Tillamook, Yamhill, Washington, Clackamas, Multnomah, and Hood River counties.
South Willamette Chapter
Draws membership from Polk, Lincoln, Lane, Marion, Linn, Jefferson, Crook, and Deshutes counties.