[1][2] This made him the youngest Australian to score a first class 150, breaking a 115-year-old record set by Clem Hill.

[1][3] Harris played semi-regularly for Western Australia over the next six years, and was even named man of the match in the 2014–15 Sheffield Shield final for scoring 81 and 158 in his two innings.

[5] His performances for the Western Australian teams frustrated coach Justin Langer, who said he was "mediocre with flashes of brilliance".

[8][9] Harris credited his newfound form with the move to Victoria, saying that the Victorian system suited him better and it was useful to have more experienced players around him than he had had in Western Australia.

In a Sheffield Shield match against New South Wales in October 2018, Harris helped Victoria to recover from a poor start of 2/6 with an unbeaten 250, the best score of his first-class career.

[12] After 25 first-class matches for Victoria, Harris had scored five centuries and averaged 47.58, and as a result of his improved consistency he was selected in Australia's Test squad for the first time.

[13] On the 23 March 2019, Harris became the 49th man to achieve the rare milestone of scoring 1,000 shield runs in a season.

He was the seventh Victorian to achieve this feat joining Chris Rogers, Matthew Elliott, Bill Ponsford, Graham Yallop, Dean Jones and David Hussey.

[15] Victoria beat New South Wales by 177 runs to win their 32nd title and Harris was named Player of the Match.

[16] On the 1 November 2020, Harris and Will Pucovski broke the 30-year record for the highest partnership in Sheffield Shield history.

[17] Harris and Pucovski combined for an astonishing 486-run opening stand against South Australia with both players recording double centuries.

The openers broke the previous record partnership of 464 held by Steve and Mark Waugh, set in a Shield match between New South Wales and Western Australia in 1990.

[18] Harris went on to win the Bill Lawry Medal for a second time as Victoria's best-performed player throughout the 2020–2021 Sheffield Shield season.

[19] Harris experienced domestic cricket in England for the first time in 2021, representing Leicestershire in the County Championship and Royal London Cup.

[13] According to Harris, he received a text message from now Australian coach Justin Langer saying, "Welcome to the brotherhood, you little bastard".

[45] Harris' batting style is typical of Perth-raised opening batsmen, similar to Justin Langer and Chris Rogers.