He was listed as having been present on roll calls until June 11, 1864 when he was captured near Trevillian Station, Va. Pvt. O'Bryan was sent to Fortress Monroe June 20th and transferred to Elmira Prison, N.Y. on July 25, 1864.
Pvt. R.S. O'Bryan was chosen for exchange and on October 11th he was paroled at Elmira and transferred for exchange. The actual exchange took place October 29, 1864.