Somerset 296 (Davies 81, Brooks 72) and 290 for 8 dec (Abell 119, Green 54) beat Glamorgan 131 (C Overton 5-38) and 166 (Cooke 82, J Overton 4-48) by 289 runs
Surrey-bound Jamie Overton marked what could prove his farewell appearance for Somerset with 5 for 48 to complete a 289-run Bob Willis Trophy victory over Glamorgan at the Cooper Associates County Ground Bristol.
Brother Craig finished with 2 for 31 and match figures of 7 for 69 as the visitors' five remaining wickets fell for 40 runs in 70 minutes on the final morning after they had resumed on 126 for 5, 329 runs behind.
Chris Cooke's battling innings took him from 67 not out overnight to 82 before Jamie Overton had the Glamorgan captain caught at first slip by James Hildreth, having faced 138 balls and hit 10 fours.
It was too little too late to save his side from a comprehensive defeat in a game they had bossed for the first two sessions. Somerset took 21 points to Glamorgan's three.
Overcast conditions and a pitch that was still responsive to quality pace bowling conspired against the visitors as the Overton twins set about finishing their opponents off.
The first wicket fell after 15 minutes when Graham Wagg chased a short, wide ball from Jamie Overton and edged a catch to wicketkeeper Steve Davies. What little hope Glamorgan had left disappeared when the same bowler, operating from the River End, produced a fine delivery to end Cooke's stubborn resistance.
At 153 for 7, Ruaidhri Smith walked out with a runner for the second time in the game, determined to contribute despite the hamstring injury he suffered while bowling in Somerset's first innings. But he could manage only three before getting a leading edge to Josh Davey, who had replaced Craig Overton, and lobbing a simple catch to Roelof van der Merwe at mid-wicket.
Jamie Overton, whose decision to reject a new Somerset contract and sign for Surrey was announced before the game, produced some jaffas in a hugely impressive spell of 7.2 overs, which yielded 3 for 16. He claimed his fifth wicket of the innings with a perfect swinging yorker, which defeated Kieran Bull's attempt to clamp down on the ball and sent his off stump flying.
Overton's celebrations suggested he had been determined to sign off his Somerset career in style before moving to the Kia Oval, and it was job done in that respect. He even had a hand, literally, is finishing the match, diving to his left to hold a slip chance offered by Michael Hogan off Jack Brooks.