There's a little info here:

BRIEF HISTORY OF THE CSA 20th TEXAS CAVALRY
by Justin M. Sanders

. . . In July 1863, the regiment was sent to the Indian Territory where it played
a major role in the battle of Honey Springs on 17 July. After Honey Springs,
the troops of the 20th served as post soldiers for Ft. Washita (near Durant
OK) and Boggy Depot (near present Atoka OK). In March, 1864 the 20th was
reorganized from an eight company regiment to a four company battalion under
the command of Maj. John R. Johnson. Companies C and D were at Ft. Washita
under Maj. Johnson, Co. B was at Doaksville (near Ft. Towson),
and Co. A was at Boggy Depot. . . .

http://www.rootsweb.ancestry.com/~txhender/Military/CivilWar/hecsa20th.html