Frost finished 72 holes at 16-under-par 272, recording his first major championship title on either the PGA or Champions Tour.
Couples was hard to shake, also notching a 68 on the final day at Shoal Creek Club to finish one shot off the pace at minus-15.
Knotted in third one shot further back were John Cook (66) and Esteban Toledo (67).
Two-time defending champ Tom Lehman fell to a 1-over 73 in the final round, finishing in a tie for 22nd at 6-under 282.
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