In the field of second and foreign language learning, how various task characteristics affect language learning has been the focus of many recent studies. Much of this research examined the relationship between task characteristics and task performance without fully taking into account learner related variables. The present study aimed to assess task complexity and sequence in relation to the learner related variables drawn from the social cognitive perspective of self-regulated learning, i.e. self-efficacy beliefs and frequency of learning strategy use, as they were applied to two versions of vocabulary learning from reading tasks. The tasks designed for the present study were based on the componential framework for second language task design. With tasks and task sequence counterbalanced, 146 first-year university students (mean age = 18.59 years) were randomly assigned to one of four groups. Results reveal a significant effect of task sequence on vocabulary learning self-efficacy beliefs, frequency of learning strategy use and task performance, and a significant interaction effect of sequence with task complexity. Findings are discussed in terms of complex interactions between task and learner factors.