As of the census[2] of 2000, there were 1,499 people, 685 households, and 474 families residing in the township.

There were 1,453 housing units at an average density of 58.3 per square mile (22.5/km2).

There were 685 households, out of which 17.7% had children under the age of 18 living with them, 61.3% were married couples living together, 4.7% had a female householder with no husband present, and 30.8% were non-families.

27.3% of all households were made up of individuals, and 16.4% had someone living alone who was 65 years of age or older.

Greenbush Township is served entirely by Oscoda Area Schools to the south in Iosco County.