On 6 June 2019, it was announced that McCowan had been given a two-year contract after getting rave reviews from the game against Partick Thistle in late April.

[6] In December 2022, McCowan would score a brace away against his former club Ayr United to help Dundee win and put them top of the Scottish Championship for Christmas.

[7] McCowan would conclude a strong season with an excellent performance and goal against Queen's Park to help Dundee clinch the Scottish Championship title.

[9] McCowan would mark his 100th appearance for the Dark Blues with an eventful performance, scoring a goal and receiving a red card in a comfortable away win over Livingston.

[13] On 30 August 2024, McCowan signed for Scottish champions Celtic on a three-year deal, for a reported fee of around £1 million.