Spatio-temporal processing (STP) is a control technique to increase the quality of the received signals in wireless networks. Outage events have a strong influence not only on the performance of the physical layer, but also on routing, MAC, and application layers. In this paper, we propose an outage-based performance analysis of collaborative STP for wireless sensor networks (WSNs). After an accurate characterization of the wireless channel, we derive the outage statistics as a function of the STP coefficients, and investigate the effects of STP on the probability, average duration and rate of the outage events. Furthermore, we show that a proper control policy for the STP coefficients can be derived according to the requirements from the application and communication layers.