The design was based on the CG-14 cargo glider but was substantially larger and featured all-metal construction.

The main undercarriage units were carried at the sides of the fuselage and were fixed, while the nosewheel was retractable.

The USAAF's experiences with cargo gliders during World War II indicated a role for a similar aircraft in the post-war inventory, but one capable of carrying a substantially heavier load and with greater recoverability than the essentially expendable wartime wooden assault gliders.

The air force eventually lost interest in purchasing assault gliders, but continued with the development of the powered variant, purchasing two more examples for evaluation as the YC-122A and redesignating the second of these as the YC-122B when the original Pratt & Whitney engines were swapped for Wright units.

The last YC-122C assault transport was flown to Tucson, Arizona, on 30 August 1955, for storage at Davis-Monthan AFB.