A hot box solar cooker with used engine oil as a storage material has been designed, fabricated and tested so that cooking can be performed even in the late evening. The performance and testing of a storage solar cooker have been investigated by measuring stagnation temperatures and conducting cooking trials. The maximum stagnation temperature inside the cooking chambers of the hot box solar cooker with storage material was the same as that of the hot box solar cooker without storage during the day time, but it was 23 degreesC more in the storage solar cooker from 1700 to 2400 h. The efficiency of the hot box storage solar cooker has been found to be 27.5%. Cooking trials were also conducted. The rice and green gram washed split were kept at 1730 h, and these were cooked perfectly by 2000 h in the hot box storage solar cooker, while these were not cooked in the hot box solar cooker without storage.