1. Introduction

2. Sample & Data Description  
2.1. The GCLASS Cluster Sample  
2.2. Spectroscopy  
2.3. Photometric Data  
2.4. UltraVISTA Field Reference  

3. Analysis  
3.1. Photometric Redshifts  
3.2. Stellar Masses and Completeness  
3.3. Rest-frame Colours  
3.4. Cluster Member Selection  

4. Results  
4.1. The Cluster Stellar Mass Function  
4.2. Cluster versus Field  
4.3. Star-forming vs Quiescent Galaxies  

5. Discussion  
5.1. The Shape of the Galaxy SMF  
5.2. A Simple Quenching Model  

6. Summary and Conclusions