Beall was an 1844 graduate of the United States Military Academy. After graduating Beall served in the United States Army. He was first assigned as a brevet Second Lieutenant with the Fourth Infantry and served on the northwestern frontier. In 1849 he was promoted to Second Lieutenant and assigned to the Fifth Infantry. He served until 1855 in the Indian Territory and Texas. He was promoted to First Lieutenant and then shortly thereafter to Captain with the First Cavalry.
At the outbreak of the Civil War Beall resigned his commission as was appointed as a Captain of cavalry in the Confederate Army. Beall served in the Trans-Mississippi Department under General Earl Van Dorn early in the war and was appointed Brigadier General in the spring of 1862.
Beall was placed in command of the Confederate cavalry forces at Corinth, Mississippi.
Beall was placed in command of a brigade made up of troops from Arkansas, Mississippi, Alabama, and Louisiana. Beall was initially in command during the Battle of Port Hudson and surrendered there on 9 July 1863. Beall was taken as a prisoner of war and imprisoned at Johnson's Island Prison Camp in Ohio.
In 1864 Beall was appointed as a Confederate agent for the purpose of supplying Confederate prisoners of war and paroled for this purpose. Beall established an office in New York, New York and sold cotton allowed through the Union blockade of southern ports. The proceeds of these sales were used to purchase clothing and blankets for Confederate prisoners in northern prison camps.