The riding was first created in 1966 with the Town of Whitby, the City of Oshawa, and part of Whitby Township, which were previously part of the riding of Ontario. In 1967, its name was changed to "Oshawa—Whitby." In the Ontario riding, the previous election was competitive, with the PCs, Liberals, and NDP all being within about 6500 votes (10%) away from each other. In 1968, the election was very close. There were over 45,000 votes cast and all 3 candidates were within 325 votes of each other. NDP candidate Ed Broadbent won, beating PC Michael Starr, who won the previous election in the riding of Ontario, by 15 votes. Broadbent and Starr would once again run against each other in the 1972 election. It was also a close race, with Broadbent beating Starr by 824 votes.