McKenzie had an unproductive tour of the West Indies in 1964–65 and had mixed fortunes in the 1965–66 Ashes series. He was not selected for the First Test, but took 5/134 in England's mammoth 558 the Second Test at Melbourne. He did little in the Third Test, which Australia lost by an innings, and was one of the five men dropped for the Fourth Test. Fortunately Peter Allan was injured and McKenzie was brought back into the team. The Adelaide Oval was notoriously flat, but McKenzie was an expert on getting batsmen out on dull wickets and used the humid atmosphere and fresh pitch to bowl Bob Barber for a duck and have John Edrich caught by the ever-reliable Simpson at slip. McKenzie took 6/48 to have England out for 241 and Australia won by an innings. He took 3/17 in the second innings in the Fifth Test to finish with 16 wickets (29.18), the chief wicket taker along with Neil Hawke who took 16 wickets (26.18). Thereafter McKenzie became one of the most consistent opening bowlers in the world.