In November 1934, Wilson was visited by an old drinking companion, Ebby Thacher. Wilson was astounded to find Thacher had been sober for weeks under the guidance of the evangelical Christian Oxford Group. Wilson took some interest in the group, but shortly after Thacher's visit, he was again admitted to Towns Hospital to recover from a bout of drinking. This was his fourth and last stay at Towns under Silkworth's care and he showed signs of delirium tremens. There, Bill W had a "White Light" spiritual experience and quit drinking. Earlier that evening, Thacher had visited and tried to persuade him to turn himself over to the care of a Christian deity who would liberate him from alcohol. He was also given belladonna, which causes hallucinations. According to Wilson, while lying in bed depressed and despairing, he cried out, "I'll do anything! Anything at all! If there be a God, let Him show Himself!". He said that in his mind's eye, that he was on a mountain and that a wind not of air but of spirit was blowing. Then he realised he was a free man. He then had the sensation of a bright light, a feeling of ecstasy, and a new serenity. He never drank again for the rest of his life. Wilson described his experience to Silkworth, who told him, "Something has happened to you I don't understand. But you had better hang on to it".
Wilson joined the Oxford Group and tried to help other alcoholics. They did not get sober, but Wilson kept sober himself. During a failed business trip to Akron, Ohio, Wilson was tempted to drink again and decided that to remain sober he needed to help another alcoholic. He called phone numbers in a church directory and eventually secured an introduction to Bob Smith, an alcoholic Oxford Group member. Wilson explained Silkworth's theory that alcoholics suffer from a physical allergy and a mental obsession. Wilson shared that the only way he was able to stay sober was through having had a spiritual experience. Smith was familiar with the tenets of the Oxford Group, and upon hearing of Wilson's experience, "began to pursue the spiritual remedy for his malady with a willingness that he had never before been able to muster. After a brief relapse, he sobered, never to drink again..." Wilson and Smith began working with other alcoholics. After that summer in Akron, Wilson returned to New York where he began having success helping alcoholics in what they called "a nameless squad of drunks" in an Oxford Group there.
In 1938, after about 100 alcoholics in Akron and New York had become sober, the 'fellowship' decided to promote its program of recovery through the publication of a book, for which Wilson was chosen as primary author. The book was given the title Alcoholics Anonymous and included the list of suggested activities for spiritual growth known as the Twelve Steps. The movement itself took on the name of the book. Bill incorporated the principles of nine of the Twelve Traditions, (a set of spiritual guidelines to ensure the survival of individual AA groups) in his foreword to the original edition; later, Traditions One, Two, and Ten were clearly specified when all twelve statements were published. The AA general service conference of 1955 was a landmark event for Wilson in which he turned over the leadership of the maturing organization to an elected board.
In 1939, Wilson and Marty Mann visited High Watch Farm in Kent, CT. They would go on to found what is now High Watch Recovery Center, the world's first alcohol and addiction recovery center founded on Twelve Step principles.
Wilson strongly advocated that AA groups have not the "slightest reform or political complexion". In 1946, he wrote "No AA group or members should ever, in such a way as to implicate AA, express any opinion on outside controversial issues – particularly those of politics, alcohol reform or sectarian religion. The Alcoholics Anonymous groups oppose no one. Concerning such matters they can express no views whatever." Reworded, this became AA's "Tradition 10".