A growing body of literature recognizes the importance of examining research article (RA) abstracts in particular disciplines. RA abstracts, after titles, are the first mini texts that readers may encounter in a scientific paper. Abstracts, therefore, determine the value of the paper and categorize them as good or vague. The present contrastive study aims to investigate the rhetorical organization of RA abstracts published in native and non-native English-speaking countries. It adopts Hyland's (2000) rhetorical structure model: introduction, purpose, method, product, and conclusion. A corpus of eighty RA abstracts written in the fields of humanities (education and sociology) and science (electronics and agronomy) and published in Ecuadorian and American journals between the periods of 2010-2016 constitutes the target data for the analysis. The results show rhetorical variation in the construction of RA abstracts across the four disciplines. These abstracts followed a non-hierarchical five move structure with three stable moves, as of M2, M3, and M4 sections. Research findings add to the claim that in academic writing, different discursive conventions and discourse community practices influence writers' preferred rhetoric and composing patterns.