Currently, the OIC has 57 member and 5 observer states
The Organization of the Islamic Conference (OIC) is an international organization grouping fifty seven states which have decided to pool their resources together, combine their efforts, and speak with one voice to safeguard the interests and secure the progress and well-being of their peoples and of all Muslims in the world.
A Map of Member States:
Countries in green are member states; countries in red are observer states; blocked states are blue.
By M.WongM (Own work), via Wikimedia Commons.