St Peter's has an aisled nave, central tower and chancel with a N chapel. The nave has original 12thc. features in one S window and N and S doorways (the N remodelled in the 13thc. and set under a modern porch; the S blocked to convert it to a window). The nave was extended westwards by some 20 feet (6 m) in 1861-63 by J. F. Clark of Norwich. There is an 18th-19thc. brick N chapel at the E end of the nave. The chancel has been rebuilt with a lowered roofline and a brick E wall, the side walls are rendered, but the E and S windows and the N doorway are 18th-19thc. and the entire chancel must be of this date. The 12thc. tower is a substantial flint structure with a later embattled parapet. There are small lancets at two levels of its lower storey on the N and S faces, and 12thc. single bell-openings in the set back upper storey. The angles of the upper storey have shafts. Inside, it has tower arches to E and W. Construction is generally of flint, except for the 18th-19thc. N chapel and chancel, which are of brick. There are a few courses of brick alternating with the flints around the SW angle of the tower's upper storey. Romanesque sculpture is found in the two nave doorways, the tower bell-openings and the tower arches.

According to the Domesday Survey, Ousden was held by thegn Leofric in the Confessor's time, and in 1086 it was held by Count Eustace. There was a church with 30 acres of free land. An annual market and a fair were granted to William de Criketoft in 1254, to be held at the manor.

Bansfield benefice, i.e. Cowlinge, Denston, Lidgate, Ousden, Stansfield, Stradishall and Wickhambrook.

A complete 12thc. central tower is a rare survival, and it is most unusual that even the bell-openings should have survived. Even within, there are no inappropriate liturgical arrangements to disrupt the original architecture.