Five second half goals for Watford meant the Cherries finished their first away game of the season with a 6-1 defeat.
The visitors were the better team in the opening period with Lewis Grabban getting the final touch on a slick team move to cancel out Gabriele Angella’s opener.
But last season’s Championship play-off finalists claimed all three points with some clinical finishing after the interval.
Defender Angella scored another before Troy Deeney and Lewis McGugan added to the Hornets' total.
Deeney then scored two more, including an injury time penalty, to complete his hat-trick.
Eddie Howe made five changes to the team that started the midweek Capital One Cup tie and two to the starting line-up that beat Charlton last weekend, which meant first league starts for Ryan Fraser and Andrew Surman.
Captain Tommy Elphick missed the fixture at Vicarage Road with a back problem, while summer signing Mohamed Coluibaly didn’t travel with the squad.
The Cherries manager predicted an open and entertaining contest in his pre-match press conference and was proved right with both teams creating early chances.
McGugan had a free-kick comfortably saved before Marc Pugh and Grabban went close down the other end.
It was far from a one sided game and the in-form striker was unfortunate to see his effort hit the side-netting after turning on Manuel Almunia’s weak punch.
But for all for their positive play in the opening stages, the Cherries found themselves behind when Angella swept home from close range.
The goal did little to deter the visitors and Grabban and Harry Arter had chances to put them back on level terms, while Fraser would have felt hard done by after going down in the box under the attentions of wing back Ikechi Anya.
And the pressure paid off when Grabban rounded off a wonderful team move in the 30th minute. Arter found Fraser with an incisive pass and he slid the ball across the face of goal to leave the lone forward with a simple finish.
The goal certainly altered the balance of the game and the Cherries finished the first half the better team, backed by 1,600 vocal supporters in the away end.
But they once again fell behind after two goals in three minutes from Angella and Deeney put the home side 3-1 ahead shortly after the break.
The Hornets defender again got the decisive touch on a corner before Deeney’s finish took a deflection and looped over Allsop.
It was difficult to take for the Cherries, who had played so well in then first half, and Howe responded by sending on Ian Harte and Brett Pitman.
But Gianfranco Zola’s side were proving difficult to stop and McGugan soon made it four when he found himself in some space and sidefooted the ball beyond Allsop.
Only a deflection could prevent Surman pulling a goal back, but Deeney completed the scoring with a spectacular strike and a penalty in the final few minutes.
Watford: Almunia, Doyley, Angella, Cassetti, Faraoni (Pudil 65), Abdi, Iriney, McGugan (Battocchio 75), Anya, Deeney, Forestieri (Fabbrini 68).
Unused substitutes: Bond, Ekstrand, Smith, Acuna.
Goal: Angella (13 & 53), Deeney (56, 87 & 90), McGugan (65)
Booked: Faraoni, Cassetti
Cherries: Allsop, Francis, Ward, Cook, Daniels (Harte 55), Fraser, MacDonald (Pitman 62), Arter, Surman, Pugh (O’Kane 69), Grabban.
Unused substitutes: Flahavan, Hughes, Stockley, Thomas.
Goal: Grabban (30)
Attendance: 16,295 (including 1,605 Cherries supporters)