Purpose: This study examined the quantity and complexity of speech-language pathologists' (SLPs') talk during therapy with school-aged children and explored the extent to which SLP- and session-level characteristics contribute to the variability in SLP talk quantity, grammatical complexity, and lexical complexity during therapy. Method: We used secondary data collected from 209 business-as-usual therapy session recordings collected in the fall of the school year involving 75 SLPs and 281 kindergarten, first-, and/or second-grade students. Students were receiving services for language disorder and had therapy goals targeting various domains of language. SLP talk was coded to capture various aspects of quantity and complexity. Results: SLPs with more years of experience tended to produce a lower quantity of talk, whereas higher levels of time pressure were associated with increased quantity of talk as well as grammatical and lexical complexity. In addition, session length, mean age of children, and children's phonological awareness scores were significantly associated with SLP talk quantity, grammatical complexity, and lexical complexity. Conclusions: This study adds to the evidence for the variability of SLP talk. SLP talk quantity and complexity are related to SLPs' years of experience and time pressure. Session-level predictors suggest grouping strategies for therapy sessions. [This paper will be published in the "American Journal of Speech-Language Pathology."]