Cowan finished with a career-high 31 points, adding six rebounds and six assists.
Hawkeyes center Luka Garza — the Big Ten's leading scorer — picked up two early fouls, limiting his impact.
The Terps lost to the Hawkeyes earlier this season in Iowa City.
The Terps will try to stay undefeated at home.
All three of the Terps' losses this season have been in true road games.