The Cowichan class vessels were the highest capacity vessels at the time for BC Ferries, built to accommodate increasing ridership, and to carry larger volumes of vehicles than existing ships. They were also the first large double-ended ferries built for BC Ferries. Being double-ended, they do not need to turn around in harbours, providing for faster arrival/departures at terminals.
The larger Cowichan class vessels are not as maneuverable as previous ships, which was demonstrated by the grounding of Queen of Alberni in 1979. After the grounding, Cowichan class vessels were required to operate in the slower but more maneuverable "docking" mode when transiting through Active Pass, which makes it unfeasible to operate on routes that use Active Pass. As such, they are now primarily found on routes 2, 3, and 30.
The first three vessels (Queen of Coquitlam, Queen of Cowichan, Queen of Alberni) replaced four second-hand vessels: [[BC Ferries Sunshine Coast Queen|Sunshine Coast Queen]], [[BC Ferries Sechelt Queen|Sechelt Queen]], [[BC Ferries Langdale Queen|Langdale Queen]], and the original [[BC Ferries Queen of the North|Queen of Surrey]], the latter of which was refitted to become Queen of the North. No vessels were directly retired by the final two vessels built (Queen of Surrey and Queen of Oak Bay), although they did allow for service expansion.