We used the m-averaged spectrum technique ("collapsogram") to extract the low-frequency solar p-mode parameters of low- and intermediate-angular degrees (l ≤ 35) in long time series of Global Oscillation Network Group (GONG) and Michelson Doppler Imager (MDI) observations. Rotational splittings and central frequencies have been measured down to ≍850 μHz, including predicted modes which have not been measured previously. Both GONG and MDI frequency splitting data sets were numerically inverted to extract the internal solar rotation rate. The impact of the very low-frequency observables and the differences between GONG and MDI data sets on the inversion results are also analyzed.