Musgraves premiered "High Horse", the third song from the album, on March 22, 2018, on Zane Lowe's Beats 1 Apple Radio show. On March 29, 2018, she performed "Slow Burn" on The Late Show with Stephen Colbert. Golden Hour was released on March 30, 2018, on MCA Nashville. On May 12, 2018, Musgraves was the musical guest on Saturday Night Live, performing "High Horse" and "Slow Burn". Through June and July, Musgraves was the opening act on the second North American leg of Harry Styles: Live on Tour. In September, Musgraves appeared on a rerecorded version of "There's No Gettin' Over Me" with Ronnie Milsap for his 2019 duet album. On October 2, 2018, she appeared on Jimmy Kimmel Live! as the musical guest.  In October 2018, Musgraves embarked on the "Oh, What a World Tour" in support of Golden Hour. The tour began in Oslo, Norway on October 13. In February 2019, Golden Hour won Album of the Year at the 61st Annual Grammy Awards. The same month, Musgraves released "Rainbow" as the fifth single from the album.  In April, Musgraves featured on a newly recorded version of "Neon Moon" with Brooks and Dunn for their duet album Reboot.  She also made a cameo appearance as herself in the country-music drama film Wild Rose, released in April.  In May, Musgraves made her Met Gala debut as a Barbie doll and afterwards announced she had signed with modeling agency IMG.  In August, Musgraves appeared at San Francisco's Outside Lands Music and Arts Festival, among her largest festival appearances to date.  In October 2019, Musgraves revealed that she would cover the song "All Is Found" for Frozen II.  The song plays over the end credits and is also included on the soundtrack album.