Local feed ingredients are widely available from industrial and agricultural waste byproducts. Palm oil cake (BS) and Solid ex decanter (SD) are feed ingredients produced from palm oil processing which is available in large quantities.  Palm oil cake (BS) and Solid ex decanter (SD) have  high protein content could be used as ruminant feed but  have high fat content could be decreased rumen metabolism. They also have a physical properties that are easily damaged when stored. Therefore, solid-state fermentation (SSF) technology is one way to overcome this problem. This study aims to improve the nutritional quality and digestibility of mixed feed palm oil cake and solid ex decanter (BS/SD) which is fermented by Rhizopus oligosporus mushroom. Application SSF technology for different combination of mixed feed BS/SD (70/30, 50/50 and 30/70) was carried out for 5 days which was then analyzed on the quality of the proximate, fiber fractions and in vitro true dry matter digestibility (IVTDMD) value (daisy incubator ANKOM Technology). The result showed that the mixed feed BS/SD 50/50 was the best combination with Rhizopus oligosporus inoculum with doses of 0.2, 0.4 and 0.8%. hence, this SSF technology was effective process for increasing protein content and in vitro true dry matter digestibility (IVTDMD) 60 % – 67.26% with combination BS/SD 50/50 and RO inoculoum with doses 0.2 and 0.4 percent.