Cosgrove is a good-sized village in the SE of the county, less than half a mile from the river Great Ouse that forms the border with Buckinghamshire, and which forms a loop around the village. It is now on the edge of the great conurbation of Milton Keynes. The Grand Union canal runs through the village, and the church is centrally sited, with the hall site to the S of it. Cosgrove church comprises a square W tower, a nave, a N aisle and a square chancel which is off-set to the S side of the nave. The tower appears to be late medieval, but its E arch may comprise Anglo-Saxon masonry reworked in the 13thc. Only its tall, narrow proportions betray the possibility that the nave is Anglo-Saxon. The E and S walls of the rebuilt neo-Norman chancel incorporate traces of 12thc. arcading, probably representing blocked windows; two medieval corbels have been re-set in its internal walls. The early 13thc. N arcade comprises quatrefoil piers with moulded capitals carrying pointed, chamfered arches with a sawtooth label. The pointed, chamfered N doorway also has a label carved with sawtooth. The church was restored in 1864-5 and again in 1887.

In 1086, land in Cosgrove was divided between the Count of Mortain and Winemar. The former's holding was partly held from him by Humphrey. Winemar's holding passed at his death to Michael of Hanslope. When Michael died c.1131, leaving Henry I as his heir, the king gave his estates to William Maudit, the king's chamberlain. The gift was confirmed in 1153 by Henry duke of Normandy (later King Henry II). The barony remained in the hands of the Maudit family until the death without issue in 1267 of William Maudit, who had become earl of Warwick in 1263 on the death of John de Plessitis. The earldom passed to William de Beauchamp, who married William Maudit's sister and heir Isabel. By 1397 the manor itself was in the hands of the Beauchamps. Cosgrove church was first recorded in 1220, when the Hospitallers were in possession of the advowson of the rectory.

The chancel was probably enlarged in the late 12thc. The original architectural design of the E wall may have comprised a triplet, with a central window flanked by lower lights, under a gable. While the technique of chip-carving was common in the late 11thc., here it appears to represent an early form of dogtooth, possibly indicating a late 12thc. date (c.1180). Although sawtooth was used as a decorative motif in the construction of the N aisle, other features confirm a date in the mid-13thc. for that work. The head corbels re-set in the chancel are considered to be 'of late medieval origin' by RCHME.