There were a number of other consolidations and collabrations between Unitarian and Universalist organizations which paved the way for the consolidation of the American Unitarian Association and the Universalist Church of America. A few individual churches merged and some ordained ministers held dual fellowship. The denominations under the umbrella of the Council of Liberal Churches collaborated in the areas of religious education, public relations, and publications. Among the most important considerations was in the youth movements of the two demoninations.

The 19th century saw the rise of voluntary associations in both Unitarian and Universalist churches—for example, women's associations, Sunday Schools, altar guilds, men's clubs, and youth organizations. Following the creation of similar groups for young people in other denominations, the Western Unitarian Conference, under the leadership of Jenkin Lloyd Jones, organized Unity Clubs in the late 19th century. These groups were largely literary and philosophical in nature. The youth they served were not the high school-aged youth we think of today, but people in their twenties and thirties. In the East, Universalist churches organized young people's Christian Endeavor Societies, oriented toward religion and social service. These societies, in turn, spurred the rise in the Eastern Unitarian churches of young people's guilds with similar goals.

In 1889, individual Universalist Christian Endeavor Societies organized into the Young People's Christian Union (YPCU). In 1896, the Unitarians followed suit, combining various groups into the Young People's Religious Union (YPRU). From that time on, the YPCU and YPRU met jointly in "Uni-Uni" rallies, in addition to meeting for their individual conferences.

The YPCU's great focus was missionary work, both domestic and international. In 1893 they hired Quillen Shinn as the national organizer for missionary work, and a year later began the "Two Cents a Week Plan" which asked every YPCU member to donate one dollar annually (or two cents per week) to missionary work. The "Two Cents a Week Plan" was extraordinarily successful, lasting (with several name changes) until 1927 and raising tens of thousands of dollars to spread the word of Universalism. The Unitarian YPRU was more modest in its goals. Centered largely in New England, its fundraising was done through semi-annual bazaars held in Boston, Massachusetts.

Over time, partly because the military draft for two world wars took young men away from home, the age of members began to drop. In 1894, YPCU had started the first organization for high school-age youth, the Junior Union, which after one year boasted 40 chapters nationally. In the early 1940s both YPCU and YPRU deliberately lowered their age requirements. In 1941, YPCU reorganized as the Universalist Youth Fellowship (UYF) serving young people ages 13 to 25. The following year YPRU became American Unitarian Youth (AUY) with members ages 15 to 25.

In the 20th century, the youth organizations of both denominations took similar paths. Each experienced times of growth and times of challenge in response to World Wars, the Great Depression, and tensions over generational, denominational, and social issues. From the beginning, the two organizations had shared close relations, meeting jointly, printing joint publications, and taking on service projects such as the 1930s Peace Caravans to respond to the escalating international arms race. By the 1950s they were ready to make their partnership formal. When it appeared their parent denominational bodies would merge into the Council of Liberal Churches—a precursor to the Unitarian Universalist Association—the youth organizations began the work of consolidation. The 1950 annual meetings of both youth groups selected representatives to a joint committee to explore the possibility of consolidation and what would need to happen to make it possible and desirable. After three years of joint investigation and discussion the two youth organizations merged in 1953, becoming the Liberal Religious Youth.