This study investigates the acquisition and maintenance of periphrastic and se-passives in second language (L2), heritage (HS), and (Spanish-dominant) native Spanish speakers (NS) by addressing: (i) How accessible are Spanish periphrastic passives (which also exist in English) and se-passives (unique to Spanish) for L2ers and HSs in production? (ii) Do their productions reflect fully acquired, target-like grammatical representations of these structures? (iii) How are L2ers’ and HSs’ productive and receptive performance on passives affected by linguistic experience, i.e., age of acquisition, nature of language exposure, and proficiency? While some theoretical accounts predict an advantage for HSs due to exposure to the target structures during childhood (e.g., Partial Access, Interpretability Hypothesis, Hawkins & Franceschina, 2004; Byland, 2009), others predict successful ultimate attainment by both groups albeit with initial difficulties with the se-passive for L2ers (e.g., Full Access, Schwartz & Sprouse, 1996). Contrastively, usage-based accounts (e.g., Ellis, 1994, Hur et al., 2020; López-Beltrán & Carlson, 2020; O'Grady et al., 2011; Perez-Cortés & Giancaspro, 2022, a.o.) predict an advantage for the more frequent se-passive across groups. The study consists of two web-based tasks: a structural priming (production) task and a timed acceptability judgment (receptive) task (AJT). Results from the priming task show that all groups can be primed to produce both passives. However, results from the AJT show that L2ers accept mismatched verbal agreement with se-passives to some extent, but not with periphrastic passives, consistent with the Partial Access accounts. In other words, their native-like behavior in production likely reflects a superficial, probability-based strategy, not a fully represented, target-like abstract structural representation. On the other hand, HSs perform at ceiling on both structures and converge with NSs in production and receptive abilities, suggesting robust knowledge of these structures. This dissertation constitutes the first experimental study to test both passive constructions in production and comprehension in any of these three speaker groups, offering insight into the particular abilities and pedagogical needs of L2ers and HSs and contributing to the discussion of how language is organized in the bilingual brain.