George has been a part of several artist collectives.
| 1953 – 1982: |
Vereniging Pulchri Studio |
member |
| 1956 – 1957: |
Verve |
member |
| 1956 – 1962: |
Posthoorngroep |
member |
| 1960 – 1967: |
Fugare |
founder |
| 1961 – 1966: |
Haagse Kunstkring |
president of the visual arts department |
