Surrey were not in too bad a spot against Essex when they were 42-1 in the sixth over.
But the hosts slumped to 123 all out, with Matt Critchley the pick of the bowlers for Essex, taking 3-16 from four overs and only Josh Philippe (33) scoring more than 30.
Michael Pepper hit a fine unbeaten 71 for Essex, who made light work of the run chase, knocking it off inside 17 overs.
Defeat for Surrey means they finished second behind Hampshire and surrendered the opportunity of a home quarter-final.
Hilton Cartwright and Ben Mayes produced an excellent 112-run partnership in 10 overs to rescue already qualified Hampshire’s run chase and beat Sussex by four wickets.
Chasing 187, Cartwright hit 70 from just 31 balls and Mayes ended unbeaten on 55 as the Hawks recovered from 61-5 to seal victory off the penultimate ball of the match.
Dan Hughes had scored 55 and Charlie Tear finished 40 not out for Sussex but it was not enough as the Hove side finish bottom of the group with only three wins from their 12 games.
Victory for Hampshire guaranteed a home quarter-final.
Middlesex ended another disappointing campaign with a consolation 14-run victory in their dead rubber against Kent Spitfires at Canterbury.
Zafar Gohar grabbed 3-38, including the wicket of Zak Crawley (10), as the Spitfires fell short of their victory target after Ben Geddes had top-scored with 32 in the Middlesex effort of 172-6.
