The main goal of the present study was to evaluate the effects of three different architectural forms on drying rate of Onion flakes. These different forms are, gable-even-span (SD1), four sides-pyramid shape (SD2) and hemispherical shape (SD3), which are used for drying Onion. Deterioration of considerable quantities of Onion takes place during storage operation. Various preservation methods have been employed to minimize this loss. Solar dryers were designed and constructed at Agricultural Engineering Research Institute. Air was pushed naturally through the holes under the greenhouse solar dryer passing through the agricultural products to carry out the moisture and moving it through the chimney which is installed at the top of the greenhouse solar dryer. There are two experimental operations; the first one was without using rocks (1) the second one with rocks (2) to raise the drying efficiency. The period of dring without rocks takes 45 hours but it takes 42 hours by rockes. The resulting efficiency is 68%, 72% for the (SD1), 62%, 69% for (SD2) and 57%, 68% for (SD3) for all dryers without rock and with rock respectively. The maximum moisture content removed from 81.2% to 12.05%, from 81% to 12.09% and from 81.2% to 14.7% without rock but it was removed from 80.02% to 8.67%, from 78.33% to 10.14% and from 78.59% to 13.55%with rock for the three solar dryer (SD1), (SD2) and (SD3) respectively. The total incident solar energy are 39.75, 36.96 and 32.62 kW for the three solar dryers without rock, respectively, while the three solar dryer with rock gave 46.06, 41.41 and 40.50 kW, respectively. In isolated communities, solar energy is quite often the only heat source which can be used to dry low cost agricultural products economically.