Radio-loud quasars in distant groups and clusters

We describe the first results from a programme to search for distant groups and clusters of galaxies using Molonglo radio-loud quasars at z > 0.5. We use two techniques to isolate group and cluster members. Firstly, we carry out multicolour imaging of quasar fields in order to search for the old, red, members. Secondly, we carry out sensitive narrow-band imaging to search for redshifted [OII] emission from late-type galaxies at the quasar redshift. Two systems at z > 0.7 discovered using these techniques are discussed. One is a compact group of galaxies, apparently at the edge of a larger group, and the other is a cluster centred on a quasar.