We analyzed how syntactic flexibility influences sentence production in two different languages – English and Russian. In Study 1, speakers were instructed to produce as many structurally different descriptions of transitive-event pictures as possible. Consistent with the syntactically more flexible Russian grammar, Russian participants produced more descriptions and used a greater variety of structures than their English counterparts. In Study 2, a different sample of participants provided single-sentence descriptions of the same picture materials while their eye-movements were recorded. In this task, English and Russian participants almost exclusively produced canonical SVO-active-voice structures. However, Russian participants took longer to plan their sentences, as reflected in longer sentence onset latencies and eye-voice spans for the sentence-initial Subject noun. This cross-linguistic difference in processing load diminished toward the end of the sentence. Stepwise GLM analyses showed that the greater sentence-initial processing load registered in Study 2 corresponded to the greater amount of syntactic competition from available alternatives (Study 1), suggesting that syntactic flexibility is costly regardless of the language in use.