He played 29 games in all competitions, without scoring, in his first season, the 1976–77 season. It was a poor season for West Ham who finished only two points above a relegation place in 17th place in the First Division. The following season, the 1977–78 season saw Devonshire's first goals for the club, in a 3–3 at Upton Park on 12 November 1977. It also saw him play 38 games in all competitions, scoring three goals. Unfortunately for West Ham his efforts could not prevent them from relegation to the Second Division after they finished in 20th place. The 1978–79 season saw West Ham rebuilding their side following relegation. Devonshire was a regular member of the side which finished 5th in the Second Division. He had played 41 of a possible 42 league games that season and was voted Hammer of the Season. West Ham failed to gain promotion again in the 1979–80 season. They did however reach the 1980 FA Cup Final where Devonshire collected an FA Cup winner's medal as West Ham beat favourites, holders and Cup Winners Cup finalists Arsenal 1–0 at Wembley with a single goal from Trevor Brooking from a cross by Devonshire. He had also scored a goal in a semi-final replay at Elland Road in a 2–1 win against Everton.