A technique is described for the continuous variation of the resultant retardance and effective privileged directions of a cascaded system of three optical retarders. The system consists of a rotatable retarder sandwiched between two fixed, identical, parallel retarders. The primary aim of the study was to develop a simple technique for a variable retarder for monochromatic light, but the robustness of the system for a narrow band on either side of the design wavelength was also studied. Simulated plots show that a linear variation of the effective retardance from 0 to 2Π is achievable, as is a linear variation of the effective azimuth from 0 to Π. It is also shown that these two parameters may be varied independently of each other.