The feeding ecology of the Arabian oryx (Oryx leucoryx) was evaluated in the Arabian Oryx Sanctuary (AOS) in the Sultanate of Oman. Fecal and forage analysis were used to evaluate the diet composition eaten by the oryx. The plant and fecal samples were collected from various sites within the sanctuary between July 2000 to July 2001 in seven sampling visits. The samples were examined using microhistological analysis to identify the plants eaten by the oryx and to estimate the occurrence of the cuticular fragments in the oryx fecal samples. Nutritional parameters such as dry matter (DM), crude protein (CP), crude fiber (CF) and total ash were estimated by chemical analysis of the most selected plant species by the oryx (five grasses and two browse species) and of the oryx fecal samples. The microhistological analysis and chemical composition of the plants and feces were both used to interpret oryx foraging habits in response to the seasonal variation. The diet of the oryx consisted of a mixture of grasses, forbs, herbs and shrubs. Microhistological analysis of the oryx fecal samples revealed that the Arabian oryx is predominantly a grazer ruminant. Of the total epidermal fragments identified in the oryx feces throughout the study period, monocotyledons and dicotyledons were 62% and 37%, respectively. Out of 41 different plant species in the AOS, twenty plant species of which ten were monocotyledons and ten dicotyledons were positively identified in the oryx feces. The occurrence of plant species in the oryx feces appears to follow the rainfall pattern. During the rainy period, consumption of the monocotyledon species increased while the dicotyledon species decreased, whereas an opposite trend occurred during the dry period. This was accompanied with the seasonal variation in the chemical composition of the DM, CP, CF and total ash levels of plants and feces. During the dry period, the DM, CF and total ash were at their highest levels while the CP was at it's lowest levels in both the plant and fecal samples. An opposite trend was observed during the wet period. The microhistological analysis of feces showed that the oryx changed it's foraging habits from one period to another. During the dry period, monocotyledons and dicotyledons were 23% and 77%, whereas during the wet period they were 81% and 19%, respectively. Generally, dicotyledons had higher CP and lower DM, CF and ash levels than monocotyledon species during both dry and wet periods. This study showed that the plant species selected by the Arabian oryx is probably a function of forage availability and palatability.