Osage Beach is located at (38.138354, -92.648678).
According to the United States Census Bureau, the city has a total area of 10.1 square miles (26.2 km²), of which, 9.4 square miles (24.3 km²) of it is land and 0.7 square miles (1.8 km²) of it (7.02%) is water. The city is located on the shores of the Lake of the Ozarks.
As of the census of 2000, there were 3,662 people, 1,687 households, and 1,035 families residing in the city. The population density was 389.8 people per square mile (150.4/km²). There were 4,055 housing units at an average density of 431.6 per square mile (166.6/km²). The racial makeup of the city was 97.35% White, 0.76% African American, 0.41% Native American, 0.49% Asian, 0.16% from other races, and 0.82% from two or more races. Hispanic or Latino of any race were 1.20% of the total population.
There were 1,687 households out of which 19.1% had children under the age of 18 living with them, 51.2% were married couples living together, 7.2% had a female householder with no husband present, and 38.6% were non-families. 31.6% of all households were made up of individuals and 10.9% had someone living alone who was 65 years of age or older. The average household size was 2.09 and the average family size was 2.58.
In the city the population was spread out with 16.0% under the age of 18, 7.4% from 18 to 24, 26.9% from 25 to 44, 29.3% from 45 to 64, and 20.3% who were 65 years of age or older. The median age was 45 years. For every 100 females there were 96.8 males. For every 100 females age 18 and over, there were 94.9 males.
The median income for a household in the city was $38,448, and the median income for a family was $49,554. Males had a median income of $30,444 versus $21,440 for females. The per capita income for the city was $22,685. About 4.5% of families and 6.7% of the population were below the poverty line, including 5.3% of those under age 18 and 6.4% of those age 65 or over.