Libben and Titone (2009) recently observed that cognate facilitation and interlingual homograph interference were attenuated by increased semantic constraint during bilingual second language (L2) reading, using eye movement measures. We now investigate whether cross-language activation also occurs during first language (L1) reading as a function of age of L2 acquisition and task demands (i.e., inclusion of L2 sentences). In Experiment 1, participants read high and low constraint English (L1) sentences containing interlingual homographs, cognates, or control words. In Experiment 2, we included French (L2) filler sentences to increase salience of the L2 during L1 reading. The results suggest that bilinguals reading in their L1 show nonselective activation to the extent that they acquired their L2 early in life. Similar to our previous work on L2 reading, high contextual constraint attenuated cross-language activation for cognates. The inclusion of French filler items promoted greater cross-language activation, especially for late stage reading measures. Thus, L1 bilingual reading is modulated by L2 knowledge, semantic constraint, and task demands. (Contains 1 footnote, 9 tables, and 2 figures.)