There are
323 mi
from Oshkosh, WI to Decatur, IL
That's the driving distance. It would take 6 hours 11 mins to go from Oshkosh, Wisconsin to Decatur, Illinois.
The flight distance (direct flight from Oshkosh, WI to Decatur, IL) is 289.89 mi.
323 mi = 520.51 kms