In this proposal we request 4 days of beamtime on GEM to study four new transition metal oxyselenide materials. Two new layered oxyselenides, La2O2Se2Mn and La2O2Se2Fe have been prepared and we request time to study their crystal and magnetic structures at room temperature and on cooling. In addition, we have discovered a new three-dimensional structure type and have synthesised both manganese and iron oxyselenide analogues. We wish to investigate their structure and magnetic behaviour as a function of temperature.