Mobile Ad hoc networks typically use a common transmission power approach for the discovery of routes and the transmission of data packets. In this paper we present PCQoS, a power-controlled QoS scheme for wireless ad hoc networks which builds QoS mechanisms for specific applications that wish to tradeoff better QoS performance for sub-optimal paths. PCQoS allows selected flows to modify their transmit power as a way to add and remove relay nodes from their paths in order to coarsely modify their observed application QoS performance. We present simulation results and show that PCQoS can be used to provide coarse control over traditional QoS metrics (e.g., delay, throughput). To the best of our knowledge the PCQoS protocol represents the first attempt to use variable-range transmission control as a means to provide QoS differentiation to applications in wireless ad hoc networks.