Quadrangle, about 6 metres south of Montacute House, and walls enclosing car park to south

The quadrangle, located about 6 metres south of Montacute House, consists of a range of buildings and walls that form a U-shaped layout. This structure dates back to the 16th century and was modified in the mid-19th century. It is constructed from Ham stone, primarily in ashlar, and features Welsh slate monopitch roofs with safe rooflights.

The north range includes a throughway and two four-light hollow-chamfer mullioned windows; one has four-centre arched lights with incised spandrils, while the other has had its mullion removed and replaced with a casement. The east range contains two two-light and two three-light mullioned windows, along with three four-centre arched doorways—two of which are moulded, and one is heavily chamfered. The south range features two four-light windows and one single-light window.

High-level windows on the east face of the east range suggest that this section was originally two-storey. A new service court was designed for this area by Lewis Vulliamy but was never built; instead, the existing service court was remodelled by 1853, resulting in the lowering of the former buildings. The walling to the south, which encloses the main car park, likely enclosed a more formal garden in 1782. These walls are approximately 2.5 metres high and made of coursed Ham stone rubble, with some sections set even higher, particularly to the south. There are 20th-century gateways in the south and west walls.