In January 1975, Brian Clough became the new manager of Nottingham Forest. Peter Taylor, who had been his assistant at Derby County during their Football League championship in 1971–1972, joined him in the summer of 1976. Taylor’s arrival caused Forest to quickly improve. On September 25, 1976, Forest signed Withe, a 25-year-old player who would make his club debut that day. In a 5-1 Football League Division Two home victory against Carlisle United, he scored on his debut alongside striking partner John O’Hare. On November 3, 1976, Withe received a new strike partner in a 2-0 Anglo-Scottish Cup victory at Ayr United. Withe’s height, strength, and power were complemented by Tony Woodcock’s speed and anticipation in the front two after he was called back up to the first team. At Ayr, Withe and Woodcock both scored. Despite making his season debut in November, Withe finished the year as the club’s leading scorer with 19 goals, followed by Woodcock with 17 goals and Player of the Year honours for Forest. In December of that year, Forest won its first trophy during the Clough and Taylor era by defeating Orient over two legs in the Anglo-Scottish Cup final. Withe participated in the 1-1 away first-leg tie on December 13, 1976, but missed the 4-0 second-leg victory due to a two-week absence from the team. Forest finished third in Division Two and was awarded promotion to the top division at the end of the season.
With Forest, Withe and Woodcock won the Football League Cup and First Division in 1977–1978. With 19 goals apiece, they finished the year as Forest’s joint leading scorers. On August 12, 1978, Withe scored in a 5-0 victory over Ipswich Town in the FA Charity Shield. Just before he turned 27 at the end of that month, Forest decided to sell him for £225,000 after he participated in the 1-1 league home draw the following week against Tottenham Hotspur. In 99 competitive first team games for Forest, Withe scored 39 goals. In 75 league games, 28 goals were scored. Steve Elliott, who was playing in his first league game, took his position in the following three games, all of which were scoreless. The 22-year-old Garry Birtles was subsequently given the number 9 jersey. He quickly established himself as a regular first choice and helped Forest win the European Cup in this season and the season after.