Only five miles N of Oxford, Yarnton is outside the city in a quiet rural situation. St Bartholomew’s was originally a small Romanesque church of nave and chancel. It was expanded in the C13th by the addition of a four bay arcade. The present S aisle may represent the Romanesque nave, as its S wall preserves a plain late C12th doorway, and also two deeply splayed windows, now with C19th lights. The N wall of the chancel has a round-headed window, possibly reusing C12th stonework. In 1611 Sir Thomas Spencer had a spacious chapel built as a setting for the family monuments, E of the S aisle and alongside the chancel. The Romanesque font is now sited within it.

The earliest documentary evidence of St Bartholomew's is from the mid-C12th when it was referred to as a chapel of Eynsham Abbey. Eynsham appropriated the church probably in 1235, and held the advowson of the vicarage until the Dissolution. Benefice of Begbroke, Yarnton and Shipton-on-Cherwell.

The claim that the present S aisle was the original nave is unproven, based on the appearance of the rough stonework there. The VCH points out the existence of similar masonry at the W end of the present nave. However, the evidence of the location of the Romanesque doorway and two windows with deep splays to the S in the S aisle seem more convincing. It is probable that the splayed window in the NW wall of the chancel, with re-used stone externally, is not in its original position.

The font here is plain, like others in the area, although the tapering profile is typical of both sculptured and plain examples in the county.