Effects of phonetically variable input (PVI) for processing instruction (PI) training and the number of training items were tested with a picture-selection eye-tracking task. Intermediate second language (L2) learners of French (n = 174) were tested before and after they received either a short (24 items), medium (48), or long (96) training on the causative structure with either single- or multivoice input. PI improved picture-selection accuracy from about 10% to above 50% regardless of the training size. Eye-tracking data showed a reduction in looks to the incorrect picture only after the short and medium training: it surfaced regardless of voice variability after the short training, whereas multivoice training led to a greater reduction after the medium training. Long training did not yield a reliable reduction of incorrect looks regardless of voice variability. Taken together, PVI does not hinder L2 syntactic learning. Learners may benefit more from a relatively shorter training with PVI.