The Central Park-St Brendan's product, playing in his second first-grade match, was in exceptional touch, making 111 off 160 balls for Geelong as his side took control of the two-day contest against Essendon at Windy Hill.
Brother Tyler had fallen for seven as the Cats slumped to 3-13 early, but by the time Josh got to the crease they were back in control at 4-102 and that dominance only increased as he played the best innings of his life.
Geelong made 258 before being bowled out, while Essendon made 1-37 in 13 overs before stumps.
It was Josh's third century of the season and fourth in Premier Cricket, now with 566 runs at 94.3 for the campaign.
Karramomus’ Josh McDonald chipped in with 16, while Goulburn Valley Bush Bash League marquee James Seymour took 1-43 and made 23 not out for Essendon.
Elsewhere, Central Park's Hamish Winter-Irving had a hand in Footscray's tidy win on day one against Melbourne.
Winter-Irving picked up 1-29 off 11 overs as his side skittled its opponent for 109, a total it had well and truly passed by stumps in making 6-165.
Katandra's Daniel Sartori only made four with the bat, while Winter-Irving was unbeaten on one.
And former Old Students and Karramomus talent James Billington finished a busy week with 27 at the top of the order for Prahran.
Billington's side had bowled Melbourne University out for 194, but was 5-110 in response by stumps.
Billington had spent the week with Victoria's Second XI side, where he featured in five Twenty20s.
While the Vics lost four matches and drew the other, Billington showed what he was capable of making 34 against Tasmania and 44 against Queensland.
Another Central Park product - Connor Hayes - was part of history on Saturday, but not exactly in a good way.
Hayes was one of nine victims for Dandenong and Hurley's Hotel Hound marquee James Nanopoulos, who took 9-26 for the best Premier Cricket figures in 62 years, and the first nine-wicket haul since the 1999-2000 season.
Nanopoulos took another two wickets in the second innings, now with 11-45 in a match Dandenong has already secured first-innings points in.
And Karramomus’ Andrew Poppa made 26 for Carlton's seconds as they made 191 against St Kilda, with the Saints 1-31 in reply by stumps.
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