The finding that speakers of aspect languages encode event endpoints to a lesser extent than do speakers of non-aspect languages has led to the hypothesis that there is a relationship between grammatical aspect and event conceptualization (e.g., von Stutterheim and Nuse, 2003). The present study concerns L1 event conceptualization in 40 L1 Spanish-L2 Swedish bilinguals (all near-native speakers of Swedish). Spanish and Swedish differ as regards grammatical aspect: whereas Swedish lacks this grammatical category, Spanish conveys aspect through verbal morphology and periphrasis. The principal aim of the study was to explore the relationship between productive event conceptualization patterns and receptive decoding proficiency related to aspectual contrasts. The participants were asked to provide oral L1 Spanish descriptions of video clips projecting motion events with different degrees of endpoint orientation (see von Stutterheim, 2003). In addition, they took a grammaticality judgment test concerning verb and gender agreement, verbal clitics and aspectual contrasts. Compared with baseline data from monolingual Spanish speakers, the results on endpoint encoding show that the bilinguals mention the endpoints of motion events to a higher degree than the Spanish control group does. Moreover, it was shown that the weaker the bilinguals' discrimination of aspectual errors on the grammaticality judgment test, the more prone they were to encoding endpoints. This result consequently furthers the hypothesis about the interconnectedness between grammatical aspect and event conceptualization. The results were further interpreted as indicating that the bilinguals are influenced by the Swedish-like tendency to attend to the boundedness rather than the ongoingness of events.