Andrew B. Booth's "Records of Louisiana Confederate Soldiers and Louisiana Confederate Commands" (State of Louisiana, New Orleans, 1920) contains an 1861 enrollment entry for Private O. HARRIS, Company B, 15th Louisiana Infantry. He enrolled at New Orleans on June 11, 1861. This is the only muster roll cited in Booth's "Records". Booth's archivists extracted information in the early 1900's from what is now preserved on microfilm and known as the Compiled Military Service Records. The CMSR sometimes contain more information than Booth's archivists recorded.

Dr. Art Bergeron's "Guide to Louisiana Confederate Military Units 1861-1865" (LSU Press, 1989) identifies Company B, 15th Louisiana Infantry as the "Empire Rangers" from Orleans Parish. It also identifies the "Empire Rangers" as Company D, 14th Louisiana Infantry [1st Regiment, Polish Brigade] recruited from Plaquemine Parish when this regiment first organized at Camp Pulaski near Amite, Louisiana. And it further identifies the "Empire Rangers" as 2nd Company B, 3rd Battalion of Louisiana Infantry recruited from Orleans Parish. Captain Robert A. Wilkinson is listed as the company commander of all three of these companies, hence it is the same company being moved around.

The "Empire Rangers" were originally enrolled in June 1861 at New Orleans, assigned to the "1st Regiment, Polish Brigade" at Camp Pulaski near Amite, Louisiana, and sent to Virginia. In September 1861, the "1st Regiment" was designated the 14th Louisiana Infantry and the "Empire Rangers" were transferred to the 3rd Battalion of Louisiana Infantry. Many of the companies forming the 3rd Battalion had arrived in Virginia identified as the "2nd Regiment, Polish Brigade". In August 1862, the 3rd and 7th Battalions of Louisiana Infantry were merged to form the 15th Louisiana Infantry regiment.

Dr. Bergeron's "Guide" contains a good history of the evolution of each these organizations and their combat experiences during the war.

Booth's "Records" contains information on a couple of other men surnamed HARRIS with the initial "O" in their names [Sephus O. HARRIS, Thomas O. HARRIS], but they were from Boone County, Missouri and Claiborne Parish, Louisiana.

Your family tradition that Otis HARRIS served in the commissary combined with the apparent fact that he was not carried on the "Empire Rangers" muster rolls after his initial June 1861 enrollment suggests that he transferred out of the company and battalion to another assignment.

Your record search should probably be directed towards the Confederate staff records. If you contact the National Archives by telephone, they will be better able to direct you to other record groups. http://www.archives.gov/research_room/genealogy/military/civil_war_records.html