First recorded (as “Sing in the Sunshine”) by Hoyt Axton with The Sherwood Singers (1963)
Hit versions by Gale Garnett (US #4/MOR #1/AUS #10/NZ #1 1964), The Lancastrians (UK #44 1964), Helen Reddy (MOR #12 1978).
From the wiki: “‘We’ll Sing in the Sunshine’ was written by Gale Garnett for her then-boyfriend, Hoyt Axton, and was first recorded in 1963 by Axton (‘Joy to the World‘, ‘No No Song‘) and The Sherwood Singers for the groups’ 1963 album The Happy Song. Garnett recorded her own version a year later, scoring a US Top-10 hit and reaching #1 in her native New Zealand. The song went on to win the Grammy Award for Best Ethnic or Traditional Folk Recording in 1965.
“In the UK, ‘We’ll Sing in the Sunshine’ was covered by The Lancastrians in a version featuring guitar work from both Jimmy Page and Big Jim Sullivan. Helen Reddy’s 1978 cover, produced by Kim Fowley, was issued as a single. Although it reached #12 on the MOR music chart, Reddy’s recording became the first lead single from a Reddy album to miss the Billboard Hot 100. Nonetheless, the song took on new life when Reddy sang the song on The Muppet Show while singing and dancing with Sopwith the Camel.”