Sixteen wides did not help Marist's cause.
In reply, opener Zak O'Keeffe looked to carry his team with 53 from 34 balls, supported initially by Kent Darlington (15), but wickets fell in steady intervals after that.
O'Leary (14) and Angus Dinwiddie (11), who joined the team from Collegiate, were the only other batsmen to reach double figures with Marist dismissed at the start of the 18th over.
Hobbs got O'Keeffe with a stumping and then picked up wickets throughout the middle and lower order to finish with 5-10 from his 3.1 overs.
Ritesh Verma (2-25) and Harpreet Binning (2-29) also did well, as United notably kept their sundry runs to just three.
In the Premier 2 grade, Central ITM Marton Saracens 2nd XI picked up an important seven wicket win over Watsons Real Estate United 2nd XI to move up into second place on the table.
Next round for the Premier 1 Twenty20 will be on January 13, while the Premier 2 grade will have their last round on the morning of January 27, with the finals in the afternoon.
Scoreboard
Premier 1
United 144 (M Pennefather 29, D Roulston 19, G Hobbs 18; M Engelbrecht 4-38, M O'Leary 3-19, T Redpath 2-26) bt Marist 112 (Z O'Keeffe 53, K Darlington 15; G Hobbs 5-10, R Verma 2-25, H Binning 2-29) by 32 runs.
Tech vs Marton Saracens not available.
Premier 2
United 2nd XI 79 (A Kenny 20, R Janes 17; M Transom 3-11, D Woolston 3-15, P Galpin 2-19, A Pond 2-23) lost to Marton 2nd XI 80-3 (M Transon 42no, M Maher 14no; D Holly 2-16) by seven wickets.
Collegiate vs Renegades not available.
Wicket Warriors bye.