Orson Hyde writes to Wilford Woodruff about Oliver Cowdery's rebaptism.
Orson Hyde, Letter to Wilford Woodruff, November 11, 1848, MS 1352, Church History Library
Bro. Oliver Cowdery has. . . .made Satisfaction to the church and has been voted to be rec'd by baptism. I expect to baptize him tomorrow
This indicates that Cowdery was rebaptized on November 12, 1848.