Mixbury is in the NE corner of Oxfordshire, eight miles from Bicester and six from Buckingham. The original late 12thc. church, probably of c. 1170, consisted of a chancel and nave, to which a N aisle and W tower were added in the 14thc. In the 1840s much of the church was rebuilt, reusing some windows and mouldings. The chancel arch was rebuilt as an enlarged version of the original, and the porch was given an outer doorway in the same 12thc. style. Although the S doorway itself has been restored, it is largely Romanesque, with multiple chevron and scallop capitals. The chancel arch is also described as an indication of the original.

In 1086 Mixbury was held by Roger d'Ivry of the king as 17 hides. After his death, c. 1120, it passed into the hands of the Bassett family for a short period. The St Valery family had aquired it by or before 1213, when Thomas de St Valery gave Mixbury in free alms to Oseney abbey (VCH).

The foundations of Beaumont Castle, built c. 1100, are marked by humps and bumps in a field to the NE of the church. Mixbury was made into a model village in 1874, by order of the Court of Chancery.

All Saints, Mixbury, belongs to the Shelswell benefice, comprising Cottisford, Finmere, Fringford, Goddington, Hardwick, Hethe, Mixbury, Newton Purcell, Stoke Lyne and Stratton Audley.

The Romanesque S doorway, with a 2nd order of lateral face chevron with beads, heads and other motifs nesting in the inner vees on the soffit, is comparable to the S doorway at All Saints, Earls Barton, Northamptonshire (Morrison). The doorway decoration of both churches is probably of similar date, c. 1170. Repairs in 1842 to one of the chancel windows at Mixbury revealed the rounded head of a window carved with chevron also in the style of the S doorway (VCH).

The 19thc. Norman-style outer doorway to the S porch simulates the restored decoration over the chancel arch, with chevron and cylindrical billet.