East Torrens posted 6/264 from its 50 overs at Karen Rolton Oval and it proved too many for University, which was dismissed for 225 at the start of the 49th over.
University won the West End Twenty20 Cup last month against East Torrens but it was unable to complete the double.
It lost three quick wickets – Ben Wakim, Will Bosisto and Campbell Vadlja – early in its chase and slipped to 5/124 after 33 overs when Michael Cormack dismissed Sam Kerber (36) and brother Daniel Kerber in quick succession.
Kyle Brazell (44) was next out and despite the efforts of Cooper Luke (27) and Ben Ellis (43 from 25 balls) the wickets kept falling.
Tate Robins took 4/33 and Luke Robins finished with 3/41.
Earlier, experienced English batter Ian Cockbain led the way for East Torrens with 81 from 77 balls but most of the team contributed to the total.
Openers Henry Dall (33) and Lewis Evans (37) gave the side a steady start against Redbacks stars Nick Winter and Joe Mennie and then Mike Cranmer (51) and Cockbain lifted the run-rate before Ryan King hit 27 later in the innings.
It was East Torrens’ first One-Day title since 2014/15.
Rain wiped out the second day of West End Premier Cricket matches on Saturday.
Five of the six games were abandoned without a ball bowled and there was one late start, with Glenelg and Port chasing first innings points.
This match also finished in a draw with Port 9/103 at stumps in reply to Glenelg’s 178.
Adelaide and Sturt secured first innings points the previous week.