This study investigates native German speakers’ and bilingual Turkish/German speakers’ sensitivity to constraints on verbal agreement with pseudo-partitive subjects such as eine Packung Tabletten (“a pack of pills”). Although number agreement with the first noun phrase (headed by a container noun) is considered to be the norm, agreement with the second (containee) noun phrase is also possible. We combined scalar acceptability ratings with a stochastic constraint-based grammatical framework to model the relative strength of the constraints that determine speakers’ agreement preferences and subsequently tested whether these models could correctly predict speakers’ verb choices in a production task. For both participant groups, number match between the container noun phrase and the verb was the strongest determinant of both acceptability and production choices. The relative ranking of the constraints that we identified was the same for both groups, and the lack of age-of-acquisition effects suggests that constraints on variable subject–verb agreement, and their relative strength, are acquirable by both early and later learners of German. Group differences were seen in the absolute constraint weightings, however, with the bilinguals’ agreement preferences being more strongly influenced by number match with the containee phrase, indicating a comparatively greater reliance on surface-level cues to agreement (such as noun proximity) among the bilingual group.