Background: Bilingual assessment is particularly difficult in the very first period of children's second language (L2) exposure. This exploratory, longitudinal study examined L2 learning after 1 and 2 years of L2 exposure by young immigrants and how it is affected by their age at first exposure to the L2 (AoE). Method: Participants were 18 immigrants ranging in age from 2;11 to 14;2 (years;months), all within their first year in Montreal at Time 1, enrolled in a French school or day care, and from a Mandarin first language background. Participants were tested again a year later. Measures included receptive and expressive French vocabulary tests and conversational language samples analyzed using traditional measures of mean length of utterance (MLU) and morphological accuracy as well as novel measures of semantic and sentence-level patterns. Results: Performance was relatively high already at Time 1 and increased significantly at Time 2 in both vocabulary and MLU. At Time 2, vocabulary scores were below normative values, whereas MLU was within expected values relative to monolingual and simultaneous bilinguals for the majority of the participants. However, higher MLUs were accompanied by more instances of both semantic errors and creative semantic strategies. French performance was strongly related to AoE; with amount of exposure equivalent, older participants outperformed the younger ones on MLU and vocabulary. Semantic errors and creative uses were strongly predicted by AoE; however, morphological accuracy and number of agrammatical utterances were not. Conclusions: This initial period of French learning involved a rapid growth spurt for most of the participants. We argue that the pattern observed, particularly among the older children, constitutes an early stage of L2 learning characterized by long utterances that are also frequently hard to understand as speakers encounter challenges and use creative strategies in their attempt to convey meaning. Comparison with normative reference bases for monolinguals and bilinguals with greater cumulative L2 exposure who have similar MLUs should be done with much caution during this early period.