1. INTRODUCTION  
2. SAMPLE AND DATA  
2.1. HST observations and data reduction  
2.2. Structural parameters  
2.3. Photometric catalogue  
2.4. Spectroscopic and photometric redshifts  
2.5. Stellar mass estimates and rest-frame colors  
2.6. Cluster membership and sample selection  
2.7. Field comparison sample  
3. RESULTS  
3.1. Projected axis ratios in clusters and the field  
3.2. Reconstructing the intrinsic shapes from the projected axis ratio distributions  
3.3. Caveats  
4. DISCUSSION  
4.1. Evolution of the massive quiescent galaxies in clusters  
4.2. The effect of environmental quenching on galaxy structure  
4.3. Morphological transformation in context of the early mass quenching scenario  
4.4. The age variation in the oblate quiescent population  
4.5. Caveats - more complex morphological history?  
5. SUMMARY AND CONCLUSIONS