Essex 263 (Allison 69*, Westley 58, Browne 49, Taylor 4-59) and 110 (Critchley 20, White 6-38) beat Northamptonshire 163 (Young 37, Allison 5-32) and 163 (Berg 39, Harmer 6-49) by 47 runs
Harmer extracted prodigious turn to run through Northamptonshire's middle and lower order after Sam Cook set up the win with three wickets in two overs to shatter Northamptonshire's hopes of chasing 211.
Harmer finished with 58 wickets for the season, one ahead of Kyle Abbott of Hampshire while Cook passed 50 for the season at an average of just 16.1.
Essex had resumed on 63 for 5 in the morning, in perfect overcast bowling conditions with White taking full advantage and obtaining plenty of movement outside off-stump.
He struck early when Michael Pepper edged a low catch to Emilio Gay at second slip and Gay was in action again when Harmer (16), who had played a few lusty blows, played a wild slash and edged White into the cordon.
White claimed his second career five-fer when he trapped Shane Snater lbw and then recorded his best figures when the ball flew once more to Gay who took a tumbling catch to dismiss Matt Critchley (20). White's figures eclipsed his previous best of 5 for 14 achieved against Lancashire in July. Tom Taylor then wrapped things up when he nipped in to claim the wicket of Cook.
In the run chase, Snater and Cook bowled a probing spell with the new ball before lunch, making an early breakthrough when Gay prodded at one outside off-stump from Snater and edged behind.
Vasconcelos got off the mark with a streaky four down to third but found the boundary off consecutive balls from Snater in the over before lunch including a glorious drive through the covers.
Northamptonshire began the afternoon session with a flurry of boundaries with Vasconcelos crunching the ball through extra cover and finding the ropes three times in one expensive over from Cook.
Will Young was soon into his work and greeted Harmer by hitting him over his head for another boundary. Harmer had his revenge later in the over though when he got one to turn sharply out of the rough. Young shaped to pad it up only for the ball to spin past his legs and smash into leg stump.
That wicket sparked a Steelbacks collapse. Vasconcelos attempted to pull Cook but the ball did not bounce as much as he expected and hit the top of his off-stump. Rob Keogh left Cook's next delivery which nipped back and trapped him lbw. Northamptonshire had lost three wickets in four balls.
Wickets continued to fall with Cook striking again in his next over when Luke Procter edged behind to leave Northamptonshire's hopes in tatters.
James Sales was the next to go, adjudged lbw to Harmer to a ball which looked like it would have gone over the stumps. Saif Zaib struck three boundaries before he was next to go, leaving a ball from Harmer which spun back and hit the stumps with the Steelbacks reeling on 93 for 7.
Berg took the offensive approach, clubbing Harmer through the covers for two boundaries and hitting a six all off one over and he continued to take the attack to the spinner as he was joined in a partnership of 49 with Taylor who also looked to be positive during his 26. Taylor eventually departed after coming down the wicket to Harmer and giving Nick Browne an easy catch at short-leg.
Berg then fell in similar fashion with Browne taking an excellent diving catch before White was the last batter to go, trapped lbw by Harmer.