The complex permittivity of beef samples with varying fat content over a fixed frequency range was evaluated using dielectric probe and waveguide cell techniques for the first time in microwave and millimetre wave ranges. The dielectric probe method has proven useful for determining the complex permittivity over a wide frequency range and establishing that frequencies in the band 8–12 GHz are suitable for more detailed analysis using a narrowband waveguide cell. The waveguide cell technique has shown a nearly linear relationship between complex permittivity and fat content. Plots of permittivity against fat content show good potential for the method to be accurately calibrated to meet the requirement of the meat industry. The influence of temperature and density on the sample complex permittivity has been established and procedures can be adapted to reduce or eliminate any dependence. This study suggests that there is great potential for the use of microwave sensors in the meat industry, however, the research only studied one species of meat taken from one anatomical location within the animal. Therefore, further research is needed to explore the full potential of this method on a broad range of meat and meats products.