The great American musical Oklahoma! has never been performed on the Westport Country Playhouse stage, yet the Playhouse played a critical role in its genesis. In 1940, a production of Lynn Riggs, play Green Grow the Lilacs incorporated turn-of-the-century folk songs and a scene with a square-dance. Theatre Guild producer Theresa Helburn suggested to the Langners that it would make a good musical. The three invited the renowned composer Richard Rodgers, who lived not far from Westport, to see a performance. Three years later the Guild was producing Oklahoma! on Broadway, based on Green Grow the Lilacs. Another beneficiary of Richard Rodgers, attendance that summer night in 1940 was the choreographer of the square-dance, a young actor named Gene Kelly. Only a few months later Rodgers cast him in the starring role in Pal Joey and a legendary musical career was born.

Several years later Westport Country Playhouse played a similar role in another musical classic. In 1952, Alan Jay Lerner and Frederick Loewe, who had achieved great success with Brigadoon and Paint Your Wagon, were struggling to create a musical from Shaw's Pygmalion. Years later Lerner wrote, "The Guild, which ran the Westport Playhouse in Connecticut, decided it would help all of us if we could see Pygmalion again on the stage and included a production of it during the summer season. It was a joy to see again." Four years later My Fair Lady became a smash hit on Broadway.