This paper studies structural convergence between two Romance languages that are in close contact. More specifically, it analyzes the differences in clitic realization and object omission in Spanish and Catalan. While in Spanish it is possible to omit phrases corresponding to direct objects based on their definiteness (Campos, 1986; Clements, 2006) and not to their syntactic position, Catalan does not regularly omit object pronouns but requires the use of the partitive en with indefinite antecedents. A five-point Likert scale grammaticality judgment task adapted from Bruhn de Garavito & Guijarro-Fuentes (2002) was designed to measure the acceptability of different object expressions in 70 different constructions in Spanish by monolingual native speakers (n = 44) and Catalan-Spanish bilingual speakers (n = 34). In the task, participants read a short dialogue containing a question and a short answer and were asked to rate the naturalness of the answer. Linguistic variables included the type of syntactic structure (simple or complex clauses), the semantic properties of the referent (+/- definite), and the grammaticality of the utterance. Stimuli were replicated seven times per condition. Results indicated significant differences between monolinguals and bilinguals, as the latter systematically accept ample optionality concerning null direct objects. Conversely, differences according to language dominance in the bilingual group could not be verified. Our data allow us to discuss views on the realization of interpretable features and on bilingual variability.