Allen wrote the lyrics for the standard "Theme from Picnic", which was a No. 13 U.S. hit in a vocal version for The McGuire Sisters in 1956. The song, however, is chiefly remembered as an instrumental, often performed in a medley with "Moonglow," both songs created for the film "Picnic" in 1955. Two instrumental versions charted in the U.S. top 5 in 1956, including a No. 1 hit version by Morris Stoloff. Because he did not write the music, Allen was not credited as a songwriter on the instrumental versions.