Who was the first Beatle to convert to Hinduism?

George Harrison, the lead guitarist of The Beatles was the first Beatle to covert to Hinduism.

He was often referred to as "the quiet Beatle", Harrison embraced Indian mysticism, and helped broaden the horizons of the other Beatles, as well as those of their Western audience.

Harrison embraced Indian culture and Hinduism in the mid 1960s.

During the filming of the movie Help!, on location in the Bahamas, a Hindu devotee presented each Beatle with a book about reincarnation. Harrison's interest in Indian culture expanded from Sitar to Hinduism. During a pilgrimage to Bombay, India with his wife, Harrison studied sitar, met several gurus and visited various holy places, filling the months between the end of the final Beatles tour in 1966 and the commencement of the Sgt. Pepper's Lonely Hearts Club Band recording sessions. In 1968, Harrison travelled to Rishikesh in northern India with the other Beatles to study meditation with the Maharishi Mahesh Yogi.

In the summer of 1969, he produced the single ("Hare Krishna Mantra)", performed by the devotees of the London Radha Krishna Temple. That same year, he and fellow Beatle John Lennon met A.C. Bhaktivedanta Swami Prabhupada, founder - Acharya of the International Society for Krishna Consciousness (ISKCON). Soon after, Harrison embraced the Hare Krishna tradition (particularly japa-yoga chanting with beads), became a lifelong devotee, being associated with it until his death.

Harrison was a vegetarian from 1968 until his death.

Refer: Wikipedia