We describe an improved method for the production of recombinant Q beta replicase heterotetramer. The successful expression of the soluble Q beta RNA polymerase complex depends on the EF-Ts and EF-Tu subunits being co-expressed prior to beta-subunit expression. Efficient co-expression requires two different inducible operons to co-ordinate the expression of the heterotrimer. The complete heterotetramer enzyme complex is achieved by production of the recombinant S1-subunit of Q beta replicase in a separate host. This approach represents a facile way for producing and purifying large amounts of soluble and active recombinant Q beta replicase tetramer without the necessity of a His-tag for purification.