Warwickshire 242 (Rhodes 63, Hasan 53*, Bracewell 4-51) and 100 for 6 (Rhodes 29, Barnard 23*) beat Essex 126 (Westley 47, Hannon-Dalby 4-21, 4-28) and 215 (Harmer 50*, Hasan 4-48, Rushworth 4-62) by four wickets
Warwickshire underlined their LV=Insurance County Championship title-chasing credentials by completing a four-wicket win over fellow challengers Essex inside three days at Edgbaston.
That left a victory target of 100 and, as batting remained far from straightforward, Warwickshire had to work hard to get there, reaching 100 for 6 from 27.2 overs.
A first defeat of the season came as a jolt for Essex after their impressive display in the draw against champions Surrey last week.
Warwickshire's third win in five games continued a strong start that has far exceeded expectations after they avoided relegation by the skin of their teeth last September.
After Essex resumed on the third morning on 86 for 4, still trailing by 30, overnight pair Matt Critchley and Michael Pepper took their side in front but neither lasted much longer as three wickets fell in 15 balls. Critchley edged Hasan to Rob Yates at first slip and Rushworth pinned Pepper lbw and had Doug Bracewell brilliantly caught by Sam Hain at second slip.
Chasing 100 in a minimum of 73 overs, Warwickshire had plenty of time but Alex Davies sought to do the job quickly and fell lbw to Cook when he missed an attempt to send the ball into the River Rea.
Batting remained awkward as Essex's seamers showed their skills. Yates edged Porter into the cordon and when Bracewell produced two superb away-cutters to remove Hain and Will Rhodes in three balls, it was 65 for 4 and Essex had a glimmer of hope.
Dan Mousley and Barnard added an important 21 and, though the dismissal of Mousley and Michael Burgess in successive overs had a few home nerves jangling at 91 for 6, Barnard steered his team home with 23 not out from 28 balls.