This dissertation examines conceptual reorganisation in second language learners by comparing event construal patterns in first language (L1) and second language (L2) discourse. Previous research suggests that the way grammatical aspect is encoded in the speaker's L1 can influence how events are conceptualised in their L2 (von Stutterheim & Carroll 2006). Given the lack of consensus regarding partial (Bylund 2011a) versus zero (Schmiedtová et al. 2011) susceptibility to reorganising L1 event construal patterns in L2, the present work contributes to this resonant discussion by investigating the extent to which language-specific grammatical aspectual operators influence message planning (Levelt 1989, Habel & Tappe 1999) in three typologically diverse L1 groups and four L2 groups. More specifically, film verbalisations and picture descriptions by Czech, Hungarian and English native speakers, and Czech and Hungarian learners of English at basic and advanced levels were elicited to test (a) whether crosslinguistic event construal contrasts are attributable to the differences in the grammatical means that are available for encoding temporality in a particular L1; (b) whether learners’ degree of susceptibility to reorganising L1 principles for temporal reference in the target language changes as a function of L2 proficiency; and (c) whether event construal patterns across groups remain unaffected by changes of modality (speech vs. writing) and task type. The main novel feature lies in testing L2 learners’ ability to adjust L1 thinking-for-speaking principles (Slobin 1996) in the target language through a systematic scrutiny of four conceptualisation processes abreast (i.e. event segmentation, information selection, temporal structuring and linearization).