For WLANs, the efficiency of MAC protocol is related to throughput and power saving, which is an important item for wireless communication with limited bandwidth. Much research work has been carried out and some of the proposed schemes are effective. However, most proposals were ether based on contention mode or schedule mode and neither possessed both good characters of two methods. In this paper, we propose a MAC protocol named OSRAP that Scheduled Random access Protocol for one hop WLAN. OSRAP works in two modes, i.e., schedule and contention mode, which is able to dynamically adapt to traffic load and achieves high throughput which is close to transmission capacity in saturated case. Unlike conventional hybrid protocols, every node does not have to intentionally reset any parameter according to the changing traffic load except its queue length. A distinguishing feature of this scheme is the novel way of allowing nodes to work with low delay, as in the contention-based mode, and achieve a high throughput, as in the schedule-based mode, without complicated on-line estimation required in previous schemes. This makes OSRAP simpler and more reliable. Through our analysis results, we show that our scheme can greatly improve the probability of successful transmission which means a high throughput and low delay.