Dawid Malan struck a stunning 96 from just 88 balls as Middlesex recorded their first YB40 win of the season against Yorkshire in the debut List A match at Radlett.
Chasing 237 to win, Middlesex comfortably came home in the 36th over, with young wicket-keeper batsman Adam Rossington making 79 not out.
Eoin Morgan made a duck on his return to county action however, falling LBW first ball to Adil Rashid.
Toby Roland-Jones had earlier continued his excellent 2013 with 4/44, while James Harris took 3/54 in his eight over spell.
Phil Jaques made 81 for Yorkshire, but despite posessing a strong bowling attack featuring Rashid and Tim Bresnan, Middlesex always looked the more likely victors, and captain Neil Dexter joined Rossington to ease the hosts over the line for a six-wicket win.