Functions for total wheat production, the major agricultural crop of Gaziantep, Sanliurfa, Diyarbakir, and Mardin provinces in Southeastern Anatolian Project (SAP) region in Turkey were developed by using annual data for the 1963-1989 period. Regression analyses were carried out on the multiple-linear, quadratic, and Cobb-Douglas functional forms of total wheat production in the region effected by cultivation area, fertilizer usage, and rainfall. From the economical theories' point of view the model revealed good insight. The models were statistically significant at the 95% confidence level. Irrigation is valued quite substantially. Output elasticities of inputs are less than 1 and function coefficient is elastic. Thus input employment can be increased to increase wheat production. Further research based on factor analysis is recommended.