Ashill is a nucleated village towards the SW of the county, some 7½ miles SE of Taunton in gently undulating countryside, the church and centre of the rather dispersed village being perched at the relatively high altitude of nearly 70m above OD. The village clusters around a junction of the old road from Taunton to Ilminster, but is now bypassed by the A358. St Mary’s stands in the centre of the village. It ic built of local stone rubble, including blue lias, and has a 2-cell plan of a single-bay chancel and a 3-bay nave with N and S porches, with a W tower. The oldest parts are 12thc, including the N and S doorways and parts of the altered chancel arch. There is a 13thc window in the nave, and the chancel is substantially 14thc, although its origins are older. Apart from the top ten courses of blue lias blocks, its N wall is distinguished by relatively fine masonry: near-ashlar. As well as the local lias, this wall contains hamstone or similar, as well as bits of chert from the nearby Blackdown Hills. There are also several horizontal strings of narrow blocks. Towards the W end of this wall, several feet E of the junction with the nave, there is evidence of the W jamb of a blocked doorway. This may be the remains of a porticus. This whole wall may well be pre-Conquest, and certainly predates 1100. Neither Pevsner nor the List description recorded this feature. The two-storey tower appears 15thc in origin, but with later modifications, including a weathervane dated 1867. This may date the 19thc restoration that undoubtedly took place. Romanesque features recorded are the two nave doorways and the chancel arch with plain blind arches flanking it.

The Count of Mortain held the manor of Ashill in 1086. It was assessed at 5 hides and in addition contained 40 acres of meadow and woodland 40 furlongs long and 20 furlongs wide. The Count also held 2 hides in Ashill from the abbot of Athelney, which had belonged to the abbey before the Conquest and were inalienable.

A capital very similar to that on the E jamb of the S doorway is found on the S side of the chancel arch at Sutton Montis, some twenty miles away. English Heritage National Monuments Record investigators were unable to gain access to the church, but describe the arches flanking the chancel arch as blocked recesses for side altars.