A fragile Middlesex were blasted out for just 149 as they lost by seven wickets at Chelmsford.
Openers Nick Gubbins (22) and Dawid Malan (23) ended up as top scorers, with Essex’s Paul Walter taking 4-37 in only his second List A game.
Former England captain Alastair Cook then scored an unbeaten 67 as the supposed day-night match ended in bright sunshine, with more than 20 overs remaining.
After Middlesex were put in, Gubbins hit five fours before he getting a thick edge to Jamie Porter and a diving James Foster – playing his first match of the season – took the catch in front of first slip.
After two brief breaks for rain, Middlesex lost two wickets in five balls – Nick Compton played on before Malan wafted at Porter to give Foster a more straightforward catch.
Walter made deep inroads into the Middlesex middle-order in a spell of four wickets from 27 balls when he sent back Adam Voges (12), James Franklin (0) and John Simpson (20) in short order.
Toby Roland-Jones and last-man Ravi Patel both made 18 as the tail wagged determinedly but Essex’s task seemed a simple one, particularly when Varun Chopra and Cook moved comfortably to 49 for the first wicket.
Cook, who eased to 50 from 51 balls, and Ashar Zaidi both survived dropped catches on a day when nothing went right for Middlesex, though Patel picked up a couple of wickets.
Tom Westley chopped on to Tom Helm and departed for 15, while Ravi Bopara took three fours in an over off Patel to take Essex within 15 runs of victory in only the 26th over.
And it was Bopara who got the winning runs to leave Middlesex struggling in the South group.
This post was last modified on 13/05/2017