The OA series of mercantile convoy sailed from Southend into the Atlantic to be dispersed about about 750 nautical miles west of Lands End. At intervals, the OA convoy would join with the complementary OB series (sailing from Liverpool) to sail to Gibraltar. In this case both OA and the OB would be designated "G" and become the OG series. Even when dispersing in the Atlantic, the OA convoy would combine with the OB convoy if they met at sea. The OA series ran from September 1939 until July 1940.

OA.180 sailed with OA.79. The following convoys did not form: