It is well known that solar radiation can be used in a variety of fields, such as solar engineering, architecture, agriculture, and hydrology. It is important to investigate solar radiation, especially in a place such as Turkey, where solar-energy potential is high. Thus, in this work, monthly average global solar radiation in the Bolu (40 degrees 44 N latitude and (31 degrees 36 E longitude) region of Turkey has been obtained. This region was intentionally chosen due to the fact that measured data is scarce. In the comparison of calculated and meteorological data, a good agreement has been observed. The author's published quadratic model seems to be used to estimate monthly average daily global solar radiation for this region where the measured data is scarce.