The next sixteen destroyers built under the War Emergency Programme were the Q/R-classes (known as the 4th and 5th Emergency Flotillas). The main difference with their predecessors was the incorporation of a transom stern. Main armament reverted back to the 4.7-in QF Mk. IX guns that had been introduced in the O-class and an extra 4-in Mk. V HA could also be included in place of four torpedo tubes although this was never applied in practice. Anti-air armament began with a quadruple 2-pdr pompom but this was increased to up to eight 20-mm and/or various Bofors guns. The number of depth charges was also increased to a maximum of 130. The Q/R-classes were heavily engaged during World War II but suffered relatively low losses, particularly compared to the pre-war ships: only two of the Q-class ships were sunk, both of them in the Mediterranean. Two of the ships were completed for the Royal Australian Navy and three more were transferred after the war, in addition to one ship for the Netherlands and three for the Indian Navy. All but one of the surviving Royal Navy ships were eventually converted to Type 15 anti-submarine frigates, as were four of the Australian ships, giving them an extra lease of life.

These ships saw extensive action in World War II, particularly in the Mediterranean where two of the ships were sunk (HMS Quail and HMS Quentin). Most of them were then transferred to the Indian and Pacific Oceans later in the war, where they participated in operations around Burma and the Dutch East Indies; some of the ships that were attached to the British Pacific Fleet fought at Okinawa and against the Japanese home islands in the final months of the war.