A single server queue with optional server vacations based on Bernoulli schedules and a single vacation policy was analyzed. Unlike most of the other single server queues in which the server provides only one kind of service, it is assumed that the server provides two types of heterogeneous exponential service and a customer may choose either type of service. Under the single vacation policy, it is assumed that whenever, the server takes a vacation, it is always a single vacation with exponentially distributed vacation period. Explicit steady state results are obtained for the probability generating functions of the queue size and the system size, the expected number of customers and the expected waiting time of customers in the queue and the system and some known results have been derived as particular cases. A numerical example is discussed.