Reeling at 63/7, experienced pair Chris Beaton (18 runs off 57 balls) and Dougald Munro (33 off 37) made a spirited fightback before Leeston-Southbridge crumbled to be all out for 113 in the 39th over.
Greenslade finished with the fine figures of 3/18 off his maximum nine overs, while Foulkes claimed 2/17 off his nine.
Will Williams took the new ball to try and make early inroads in defending the under-par total, and while he got the big wicket of Foulkes, caught behind for just 13, Leeston-Southbridge could do little to deny Darfield.
Opener Nick Gilbert batted supremely for an unbeaten half-century, well-supported by a free-flowing 32 off 37 balls from Ryan Hughes who took out MVP honours, and guided Darfield to an eight-wicket, with 16.3 overs to spare.
In the plate final, Lincoln chased down Oxford-Rangiora's 155 with four wickets in hand in a well-fought contest to end their season on a high note.
Short scorecard:
• Leeston-Southbridge 113 (D Munro 33, B Hill 20; W Greenslade 3/18, Z Foulkes 2/17, R Hughes 2/18)
Lost to Darfield 116/2 (N Gilbert 53no, R Hughes 32no).
• Oxford-Rangiora 155 (D Fulton 68, L Waghorn 23, A Singh 20; T Holland 4/33, B Moore 2/21, E Paterson 2/46)
Lost to Lincoln 156/6 (H Drummond 63, A Paterson 29no; H Sail 3/2, A Singh 2/37).