Tasks provide engaging ways to involve learners in meaningful, real-world activities with the foreign language (FL). Yet selecting classroom tasks suitable to learners' linguistic readiness is challenging, and task-based research is exploring the relationship between learners' overall abilities (e.g., reading, grammatical) and the complexity and accuracy of their production (Skehan and Foster 2012). The present study examines the effects of learners' reading abilities prior to a task and reading behaviors during the task on their production of linguistic complexity and accuracy. Fifty third-year, university-level FL learners of Spanish participated in two tasks. In each, they first explored a 3D world to seek clues to a mystery, after which pairs solved the mystery in synchronous computer mediated communication (SCMC). To gauge their reading abilities, learners completed a reading comprehension test (prior to the tasks). Technologies within the 3D world tracked learners' reading behaviors. The SCMC data was analyzed for linguistic complexity and accuracy. Regression and exploratory analyses showed that learners' production of linguistic complexity and accuracy in SCMC was the result of not just their prior reading abilities but also their reading behaviors while exploring the 3D world.