This study was designed to determine characteristics of rumen fermentation and post-ruminal protein digestion of Egyptian tanniniferous plants in comparison with two high quality roughages using gas production (GP) technique and the three steps in situ/in vitro procedures. Tanniniferous plants included Acacia saligna, Atriplex halimus, Prosopis gauliflora (pods and leaves) and Leucaena leucocephala leaves. The roughages were Trifolium alexandrinum (clover hay) and corn silage. Results showed that Prosopis leaves had the lowest (P< 0.05) cumulative gas production in comparison to other feedstuffs. While, the highest cumulative gas production was observed in corn silage, followed by L. leucocephala leaves, Prosopis pods, A. saligna leaves, hay and A. halimus leaves, respectively. The Prosopis and A. halimus leaves showed the lowest predicted feed intake (FI). The predicted metabolizable energy (ME) and net energy (NE) varied widely in the seven forages with particular high values in L. leucocephala and low values in Prosopis leaves (P< 0.05). Estimated organic matter digestibility (OMD) and microbial protein (MP) significantly differ between plants. Moreover, either leaves or pods of Prosopis had the lowest (P< 0.05) OMD and MP, while L. leucocephala leaves presented the highest (P< 0.05) OMD and MP. There were significant differences among plants in the NH3-N concentration. The A. saligna leaves showed the lowest NH3-N, while clover hay had the highest NH3-N concentration. There was non-significant difference in VFA concentrations among clover hay, corn silage, A. saligna and L. leucocephala but there was a significant difference among A. halimus and Prosopis pods and leaves. Tanniniferous plants and roughages had variable content of rumen degradable protein (RDP). The RDP content varied from 12.4% in A. saligna to 60.8% in hay. The rumen undegradable protein (RUP) differ significantly among feedstuffs. The highest values for RUP were observed in A. saligna but the lowest values were found in hay. The intestinal protein digestion (IPD) content was highest in hay and corn silage but lowest in A. saligna leaves. This study confirmed that tanniniferous plants had a potential nutritive value with different percentage of phenolic compounds, which cannot be dissociated completely post ruminally.