The language switching task has provided a useful insight into how bilinguals produce language. So far, however, the studies using this method have been limited to lexical access. The present study provides empirical evidence on language switching in the production of simple grammar structures. In the reported experiment, Polish-English unbalanced bilinguals switched between their L1 and L2 while describing pictures of ongoing and completed actions with simple SV progressive and perfective phrases. The results show asymmetrical switching costs for progressive phrases and symmetrical switching costs with reversed dominance for perfective phrases. These findings parallel those obtained in tasks requiring the production of single words, although the present study is the first in which the same bilingual participants display different patterns of switching costs depending on the characteristics of utterances they produce. These results can be explained using recently developed models of bilingual language control.