Garstang moved into second place in the table with a comfortable victory at the Riverside on Saturday.
Having won the toss and put Penwortham into bat, Garstang reaped the rewards of an excellent bowling display.
They enjoyed a great start with Gareth Walling trapping opener Martin Hewitt and number three batsman Paul Goodwin both LBW without scoring.
Jack Aspden (16) and Tim Campkin (17) led a mini-revival before both fell victim to Ian Walling and Ryan Wells respectively.
Jonathon Hothersall (5) departed quickly, again to Ian Walling.
Tom Nowlan and Andrew Tobutt also chipped in with 17 each before they were dismissed by Wells and Michael Walling.
The same bowlers also accounted for Jack Armer (6) and Neil Patel (4) before Mohammed Bilal Liaqat’s run out of Thomas Wilson (5) ended the innings.
Of the Garstang bowlers, Ryan Wells led the way with figures of 3-30, while there were two wickets apiece for Jennings (2-33), Ian Walling (2-23) and Michael Walling (2-11).
In reply, Garstang’s innings was steady rather than spectacular.
Michael Walling led the way with 27 before being bowled by Armer.
Allan Cook and Tom Wells both made 17 before they were dismissed by Patel.
Matthew Crowther (2) was run out and Mark Winstanley (1) LBW to Wilson as Mark Walling (23 not out) and Bilal Liaqat (1 not out) got them across the finishing line midway through the 31st over.
Patel had Penwortham’s best bowling figures of 2-16, while Wilson claimed 1-30 and Armer 1-19.
Victory leaves Garstang second in the table with 98 points, eight adrift of leaders Vernon Carus.
They can leapfrog the league leaders on Saturday when they travel to Vernon Carus (1.30pm) before facing Fulwood and Broughton on Sunday.
Vernon Carus are also the opposition for the firsts’ Twenty20 XI as the two sides meet at the Riverside on Wednesday (6pm).
Garstang defeated Longridge last time out, making 110-6 before bowling out Longridge for 83 in reply.