This study examined multimedia instruction (MI) effects on the development of the French prototypical and non-prototypical past forms among Hispanophone learners. During 4 weeks of classroom instruction, participants were exposed to MI in one of 4 conditions: learners at early stages of past-tense development received MI including prototypical (n = 12) or non-prototypical past-tense (n = 12) forms, and learners at late developmental stages were exposed to MI including non-prototypical (n = 17) or prototypical forms (n = 13). Before, immediately after, and 3 weeks after the experiment, participants completed 1 paper-and-pencil and 2 computerized tests. ANOVAs revealed past-tense growth among learners at early developmental stages only. Neither prototypical nor non-prototypical growth was documented among learners at late developmental stages. These findings highlight the need to consider MI design variations as learners' L2 grammar evolves.