We show that the baryonic oscillations expected in the galaxy power spectrum may be used as a “ standard cosmological ruler ” to facilitate accurate measurement of the cosmological equation of state . Our approach involves a straight-forward measurement of the oscillation “ wavelength ” in Fourier space , which is fixed by fundamental linear physics in the early Universe and hence is highly model-independent . We quantify the ability of future large-scale galaxy redshift surveys with mean redshifts z \approx 1 and z \approx 3 to delineate the baryonic peaks in the power spectrum , and derive corresponding constraints on the parameter w describing the equation of state of the dark energy . For example , a survey of three times the Sloan volume at z \approx 1 can produce a measurement with accuracy \Delta w \approx 0.1 . We suggest that this method of measuring the dark energy powerfully complements other probes such as Type Ia supernovae , and suffers from a different ( and arguably less serious ) set of systematic uncertainties .