This study takes a new look at the topic of developmental stages in the second language (L2) acquisition of morphosyntax by analysing receptive learner data, a language mode that has hitherto received very little attention within this strand of research (for a recent and rare study, see Spinner, 2013). Looking at both the receptive and productive side of grammar acquisition, however, is necessary for a better understanding of developmental systematicity and of the relationship between receptive and productive grammar acquisition more widely, as well as for the construction of a comprehensive theory of second language acquisition (SLA). In the present exploratory study, the receptive acquisition of L2 English grammar knowledge is studied cross-sectionally within a Processability Theory (PT) framework (Pienemann, 1998, 2005b), a theory of L2 grammar acquisition which makes explicit predictions about the order in which L2 learners learn to productively process different morphosyntactic phenomena. Participants are 72 francophone beginning child L2 learners (age 6-9) acquiring English in an immersion program. The learners' ability to process six morphosyntactic phenomena situated at extreme ends of the developmental hierarchy proposed by PT was tested by means of the ELIAS Grammar Test, a picture selection task. Overall, the developmental orders obtained through implicational scaling for the six target phenomena agreed with PT's predictions, suggesting that similar mechanisms underlie the acquisition of receptive and productive L2 grammar processing skills.