This anglophone learners' corpus study in Spanish as a foreign language aimed at analysing error etiology in the use of grammatical collocations verb + preposition in proficiency levels A2 and B1. A collocational error taxonomy was used to determine the source (intralingual and interlingual) of the cognitive mechanisms leading to the error by contrasting English-Spanish collocational equivalents. The findings show a greater number of interlingual errors in both levels, which include collocative false selection or omission of the collocative, and collocational addition errors. Nevertheless, overgeneralization error frequency in level B1 surpasses level A2 in intralingual mechanisms. This would reveal greater impact of L2 (Spanish) distinctions as error cause in B1 level. This study contributes to research on the acquisition of intermediate fixedness phraseological units, particularly, to the explanatory aspects of grammatical collocation errors in anglophone learners of Spanish as a foreign language.