Eye movements provide a sensitive window into cognitive processing during reading. In the present study, we investigated beginning readers longitudinal changes in temporal and spatial measures of eye movements during oral versus silent reading, the extent to which variation in eye movements is attributable to individual differences and text differences, and the functional form of growth trajectories of eye-movement variables. Data were from 363 English-speaking children (52% male; 59.8% White) in the US who were followed longitudinally from Grade 1 to Grade 3. Results showed a rapid decrease in temporal eye-movement measures (e.g., first fixation) and an increase in spatial eye-movement measures (initial landing position) in both oral and silent reading. The majority of variance in eye movements was attributable to individual differences whereas some variance in initial landing position was due to text differences. Most eye-movement measures had nonlinear growth trajectories where fast development tapered off near the end of Grade 3 while initial fixation count and total gaze count in silent reading had a linear growth trajectory. The findings provide a first large-scale look into the developmental progression of eye movements during oral and silent reading during a critical period when reading skills rapidly develop.