O'Hare started his senior career with Sunderland, playing for the first team between 1964 and 1967.
Derby County
He then moved to Derby County for £20,000 in 1967. There was initial criticism of him as he was seen as a large but slow striker, however, their manager Brian Clough, who had coached him at Sunderland, persisted with him and in his second season he justified his fee, establishing a strike partnership with Kevin Hector as they led the Rams to the 1971–72 Football League First Division title.
After Clough's departure he fell out of favour with his successor, and former Derby captain, Dave Mackay.
Leeds United
O'Hare followed Clough from Derby to Leeds United in 1974 alongside John McGovern for £125,000; however, Clough left Leeds after only 44 days.
Nottingham Forest
O'Hare and McGovern re-united with Clough at Nottingham Forest in February 1975 for a combined fee of £130,000.[2] Forest were promoted to the top flight at the end of the 1976–77 season. In their first season back-up, Forest won the league by seven points (two points for a win) and won the 1979 European Cup Final the following season.