Oswald was given command of the frigate HMS "Bacchante" in January 1971 and then joined the staff of the Assistant Chief of the Defence Staff at the Ministry of Defence in 1972. Promoted to captain on 31 December 1973, he attended the Royal College of Defence Studies in 1976 before being given command of the destroyer HMS "Newcastle" in January 1977 and joining the Royal Navy Presentation Team in 1979. He went on to be Captain of the Royal Naval College, Dartmouth in June 1980. He was appointed Aide-de-Camp to the Queen on 7 July 1982 and was promoted to rear admiral on 2 September 1982 on his appointment as Assistant Chief of the Defence Staff (Programmes).