Previous experiments have demonstrated the impact of speech prosody on syntactic processing. The present study was designed to examine how listeners use specific acoustic properties of prosody for grammatical interpretation. We investigated the independent contributions of two acoustic properties associated with the pitch and rhythmic properties of speech; the fundamental frequency and temporal envelope, respectively. The effect of degrading these prosodic components was examined by testing listeners’ ability to parse early-closure garden-path sentences. A second aim was to investigate how effects of prosody interact with semantic effects of sentence plausibility. Using a task that required both a comprehension and a production response, we were able to determine that degradation of the speech envelope more consistently affects syntactic processing than degradation of the fundamental frequency. These effects are exacerbated in sentences with plausible misinterpretations, showing that prosodic degradation interacts with contextual cues to sentence interpretation.