Was the Shah of Iran overthrown by Muslim forces?

The question as worded is not helpful. The Shah was ruling a country that is overwhelmingly Moslem, therefore any force that overthrows him will be constituted of Moslems. (A similar question would be "Was Louis XVI overthrown by Christian forces?")

The question you are most likely trying to ask is "Was the Shah of Iran overthrown by Islamist forces?" where Islamists are those who seek to implement political manifestations of Islam. The Islamic Revolution did not start out as being led by the Islamists but during the late part of 1978, they began to have substantially larger role. By the time the Shah left, the Islamists led by Ayatollah Ruhollah Khomeini were able to move into the power vacuum he left and crush all of the liberal dissenters.