In April 1976 he joined Brian Clough's Nottingham Forest in England's second tier. At the end of his first full season the club were promoted to the top flight. Barrett gained a Football League title in 1978 and a League Cup winners medal with Forest in 1979. In the European Cup in 1978 he scored in the 2-0 home leg win in the first round against Liverpool. He made a total of 94 senior appearances for them (scoring 8 times).
He moved to Swindon Town in June 1980 and made 5 appearances for them (3 League, 2 League Cup) before being released in May 1981 when he joined non-leagueAndover.