In 1967, the Maharishi gave a lecture at Caxton Hall in London which was attended by Leon MacLaren, the founder and leader of the School of Economic Science (SES). He also lectured at UCLA, Harvard, Yale and Berkeley. That year, an article in Time magazine reported that the Maharishi "has been sharply criticised by other Indian sages, who complain that his programme for spiritual peace without either penance or asceticism contravenes every traditional Hindu belief". Religion and culture scholar Sean McCloud also reported that traditional Indian sages and gurus were critical of the Maharishi, for teaching a simple technique and making it available to everyone, and for abandoning traditional concepts of suffering and concentration as paths to enlightenment. At the end of 1968, the Maharishi said that after ten years of teaching and world tours, he would return to India.
In 1967, the Maharishi's fame increased and his movement gained greater prominence when he became the "spiritual advisor to the Beatles", though he was already well known among young people in the UK and had already had numerous public appearances that brought him to the band's attention. Following the Beatles' endorsement of TM, during 1967 and 1968 the Maharishi appeared on American magazine covers such as Life, Newsweek, Time and many others. He gave lectures to capacity crowds at the Felt Forum in New York City and Harvard's Sanders Hall. He also appeared on The Tonight Show and the Today TV shows.
He and the Beatles met in London in August 1967, when George Harrison and his wife Pattie Boyd urged their friends to attend the Maharishi's lecture at the Hilton on Park Lane. The band members went to study with the Maharishi in Bangor, Wales, before travelling to Rishikesh, India, in February 1968 to "devote themselves fully to his instruction". Ringo Starr and his wife Maureen left after ten days, Paul McCartney and Jane Asher left after five weeks; the group's most dedicated students, Harrison and John Lennon, departed with their wives sixteen days later. During their stay, the Beatles heard that the Maharishi had allegedly made sexual advances towards Mia Farrow. On 15 June 1968, in London, the Beatles formally renounced their association with the Maharishi as a "public mistake". "Sexy Sadie" is the title of a song Lennon wrote in response to the episode. Lennon originally wanted to title the song "Maharishi", but changed the title at Harrison's request. Harrison commented years later, "Now, historically, there's the story that something went on that shouldn't have done – but nothing did." In 1992, Harrison gave a benefit concert for the Maharishi-associated Natural Law Party, and later apologised for the way the Maharishi had been treated by saying, "We were very young" and "It's probably in the history books that Maharishi 'tried to attack Mia Farrow' – but it's bullshit, total bullshit." Cynthia Lennon wrote in 2006 that she "hated leaving on a note of discord and mistrust, when we had enjoyed so much kindness from the Maharishi". Asked if he forgave the Beatles, the Maharishi replied, "I could never be upset with angels." McCartney took his daughter, Stella, to visit the Maharishi in the Netherlands in 2007, which renewed their friendship. The New York Times and The Independent reported that the influence of the Maharishi, and the journey to Rishikesh to meditate, steered the Beatles away from LSD and inspired them to write many new songs. In 2009, McCartney commented that Transcendental Meditation was a gift the Beatles had received from the Maharishi at a time when they were looking for something to stabilise them. The Beatles' visit to the Maharishi's ashram coincided with a thirty-participant Transcendental Meditation teacher training course that was ongoing when they arrived. Graduates of the course included Prudence Farrow and Mike Love.
The Maharishi had come out to teach with the "avowed intention" to change "the course of human history". When he first began teaching he had three main aims: to revive the spiritual tradition in India, to show that meditation was for everyone and not just for recluses, and to show that Vedanta is compatible with science. The Maharishi had a message of happiness, writing in 1967 that "being happy is of the utmost importance. Success in anything is through happiness. Under all circumstances be happy. Just think of any negativity that comes at you as a raindrop falling into the ocean of your bliss". His philosophy featured the concept that "within everyone is an unlimited reservoir of energy, intelligence, and happiness". He emphasised the naturalness of his meditation technique as a simple way of developing this potential.
In his 1967 publication, Bhagavad-Gita: A New Translation and Commentary, the Maharishi describes the Bhagavad Gita as "the Scripture of Yoga". He says that "its purpose is to explain in theory and practice all that is needed to raise the consciousness of man to the highest possible level." According to Peter Russell, the Bhagavad-Gita deals with the concept of loss of knowledge and subsequent revival, and this is brought out by the Maharishi himself in the introduction. In the Preface, the Maharishi writes: "The purpose of this commentary is to restore the fundamental truths of the Bhagavad-Gita and thus restore the significance of its teaching. If this teaching is followed, effectiveness in life will be achieved, men will be fulfilled on all levels and the historical need of the age will be fulfilled also."