Cockburn started home ground advantage by winning the toss and electing to bat.
They got off to a flyer, scoring 6/161 in their 40 overs with Chris Kerch-eval scoring his fourth half-century of the season with 57 runs.
Mark Natale was the pick of the bowlers, taking three of the six wickets while Elliott Lawrie took two.
Set a big total to chase, East Fremantle did it with relative ease, scoring 4/163 with seven overs to spare.
Natale proved just as lethal with the bat as with the ball, scoring a game-high 64 to steer the team to victory and the grade 1 one-day premiership.
East Fremantle were not as lucky in their Grade 3 and 5 finals, going down to CBC and Cockburn respectively.
In the Grade 3 game, CBC won the toss and elected to bat, scoring a reasonable 7/138, but East Fremantle were only able to score 123 in return before being bowled out with three overs to spare.
The Grade 5 final was a reversal of the Grade 1 game, with Cockburn able to atone and bring home a flag.
They won the toss and elected to bat first, making a respectable 139, despite being bowled out in 38.3 overs, with Anthony Every top scoring with 38 runs.
The workload was shared evenly between the East Fremantle bowlers, with Patrick Lindorff the pick nabbing 3/17 and a maiden off seven overs while Callum Strnadica, Christopher Olczyk and Jayden Kostopoulos took two wickets each.
East Fremantle were only able to score 77 in reply before being bowled out, Lindorff top scoring with 23 and Cockburn bowler Justin Micale running riot with the ball, taking five wickets to seal the result.