Abstract: Four, rumen fistulated crossbred dairy steers were randomly assigned according to a 2 x 2 Factorial arrangement in a 4 x 4 Latin square design to investigate the effect of feeding pattern and supplementation of mineralized solid palm fat (MSPF) on feed intake, digestibility of nutrients, ruminal fermentation and ruminal microbial protein synthesis. The dietary treatments were as follows: T1 = feeding with roughage and followed by concentrate after 4 h (FRC); T2 = feeding with roughage and followed by concentrate after 4 h with mineralized solid palm fat (FRC+MSPF); T3 = total mixed ration (TMR); T4 = total mixed ration with mineralized solid palm fat (TMR+MSPF), respectivity. The animals were offered urea-treated rice straw as a roughage source. Results revealed that feed-intake, digestibility of nutrients and volatile fatty acids in the rumen were similar among all treatments. As for ruminal pH and urinary purine derivatives they were significantly different among treatments and were higher in animals with roughage feeding and followed by concentrate after 4 h than with TMR diets; however, supplementation of MSPF were not significantly different among treatments. In addition, supplementation of MSPF resulted in reducing protozoal population while population of ruminal bacteria and fungal zoospores were enhanced. In conclusion, the combined use of feeding with roughage and followed by concentrate after 4 h with MSPF could improve rumen pH, microbial protein synthesis but reduced protozoal population in dairy steers.