Represented by Scott McCandless, Ross Mallon and Graham Bell, Bathgate posted a total of 223 in the better morning conditions.
But, despite being out in the afternoon rain, that was matched by Craigielaw trio Kenny Glen, Craig Davidson and Ross Colquhoun.
That meant it came down to the better inward halves and that saw Bathgate come out on top on a day when McCandles and Mallon carded 74s and Bell had a 75.
The host club, represented by Ryan Burns, Gordon Cowen and Barrie Lewis, pipped Ratho Park on a countback on 225 to finish third.
Lewis, with a 71, carded the best individual score of the day.
George Heriot’s FP, with David Campbell, Scott Dickson and Stuart Langlands in action, retained the Walker Trophy for affiliate clubs with a 231 total.