The ground-breaking transmission, which went to air on BBC2 on January 3, 1971, paved the way for four decades of partnership between the university and the broadcaster.
That relationships has produced 7,000 TV and 4.000 radio programmes in the decades which followed.
Credited with making the university a household name, the initial black-and-white broadcasts catered for the OU's first enrolment of 25,000 students taking courses in the arts, social sciences, science or maths.
The lectures, which switched from late-night broadcasts to the early hours with the introduction of video recorders, have evolved into the current range of mainstream OU/BBC programming such as Coast and James May's Big Ideas.
Dr Sally Crompton, the head of the university's Open Broadcasting Unit, said the joint programming widened access to learning and had been consist- ently recognised with industry awards.
Dr Crompton noted: "The Open University's partnership with the BBC provides a unique way to combine academic expertise and high-quality production.
"TV, radio and online content brings education to millions of people and, while it has evolved from late night programmes to mainstream television, it is still central to what the OU does, making learning accessible."
The OU received its Royal Charter in 1969 and faced widespread criticism in its early years as a result of its radical open admissions policy, which did not insist on any prior educational qualifications for students.
An estimated 300 million viewers watched the BBC/OU's programmes during 2009/10 and the distance-learning university, based in Milton Keynes, currently has more than 250,000 students, including 20,000 based overseas.