We introduce a method to constrain general cosmological models usingBaryon Acoustic Oscillation (BAO) distance measurements from galaxysamples covering different redshift ranges, and apply this method toanalyse samples drawn from the Sloan Digital Sky Survey (SDSS) and 2dFGalaxy Redshift Survey (2dFGRS). BAOs are detected in the clustering ofthe combined 2dFGRS and SDSS main galaxy samples, and measure thedistance-redshift relation at z = 0.2. BAOs in the clustering of theSDSS luminous red galaxies measure the distance-redshift relation at z =0.35. The observed scales of the BAOs calculated from these samples andfrom the combined sample are jointly analysed using estimates of thecorrelated errors, to constrain the form of the distance measureDV(z) ≡ [(1 +z)2D2Acz/H(z)]1/3. HereDA is the angular diameter distance, and H(z) is the Hubbleparameter. This gives rs/DV(0.2) = 0.1980 +/-0.0058 and rs/DV(0.35) = 0.1094 +/- 0.0033(1σ errors), with a correlation coefficient of 0.39, wherers is the comoving sound horizon scale at recombination.Matching the BAOs to have the same measured scale at all redshifts thengives DV(0.35)/DV(0.2) = 1.812 +/- 0.060. Therecovered ratio is roughly consistent with that predicted by the higherredshift Supernova Legacy Survey (SNLS) supernova data for Λ colddark matter cosmologies, but does require slightly stronger cosmologicalacceleration at a low redshift. If we force the cosmological model to beflat with constant w, then we find Ωm = 0.249 +/- 0.018and w = -1.004 +/- 0.089 after combining with the SNLS data, andincluding the WMAP measurement of the apparent acoustic horizon angle inthe cosmic microwave background.