Acceptance of 1H-MRS for clinical use is hindered by variability in methodology across platforms. Cross-vendor standardization is thus desirable for large-scale studies to be conducted. Here, we standardize a semi-LASER scheme (TE=30 ms) with identical pulses, inter-pulse durations and acquisition protocol in phantom and healthy volunteers on Philips and Siemens 3 T systems. The implemented method resulted in high quality spectra with matched SNR, linewidth and spectral patterns in phantom and similar estimated metabolite concentrations in vivo: between-subject CVs for NAA were (2.6-11.0)% and (3.3-10.2)% for Philips and Siemens, respectively. This method highlights the potential for pooling data across multiple sites.