Wycombe started brightly and Cowan-Hall forced Lenny Pidgeley in the County goal into the first save of the game as he tipped over a lopping header from a corner.
However, the Exiles dominated for the next 15-minutes with Mark Byrne testing the ‘keeper following good build up involving Mike Flynn and Robbie Willmott.
County then had a great chance to open the scoring when Rene Howe broke clear on the right and cut the ball back to Flynn, only for Wycombe’s Matthew Ingram to keep out his shot and Flynn saw his follow up blocked.
Kevin Feely was next to come close as he headed over another Willmott cross before Max Kretzschmar fired a Wanderers free-kick wide.
Left-back Joe Jacobson tried an audacious effort from the halfway line that sailed wide of Pidgeley’s goal before Feely missed another County chance before the visitors opened the scoring 40-minutes in.
It was more a case of bad County defending as Peter Murphy rose highest at the near post to head in from Kretzschmar’s corner.
And Wycombe doubled their lead just four-minutes later after more poor defending allowed Sam Wood to skip past Darren Jones and square to an unmarked Cowan-Hall, who had an easy tap in from six-yards.
Justin Edinburgh tried to change things shortly after the restart with Ismail Yakubu and Yan Klukowski coming on for Mike Flynn and Aaron O’Connor, meaning County reverted back to their old 3-5-2 formation.
That allowed Willmott more freedom down the right and he set up Minshull, only for the midfielder to send his header just wide of the post.
The second-half was largely uneventful with just Willmott and substitute Adam Chapman having half chances for the Exiles.
It will be interesting to see how many changes Edinburgh now makes for the Capital One Cup tie with Reading in midweek.
County Team: Pidgeley; Willmott, Jones, Feely, Sandell (c); Flynn (Klukowski, 56), Minshull (Chapman, 73), Byrne; Zebroski, Howe, O’Connor (Yakubu, 56)
Unused Subs: Thomas, Jeffers, Hughes, Jolley
My County MOTM: Robbie Willmott – Looked sharp at right-back with some dangerous runs and crosses going forward.