Most teachers of mathematics think that regular practice is essential for success. In face-to-face instruction settings, regular practice requires doing homework, which has to provide students with feedback in order to be useful. Online homework allows teachers to assume the workload involved in providing feedback to a large number of students enrolled in higher education. Several studies have established an association between completing online homework quizzes and learning achievement in face-to-face environments. In a fully asynchronous online environment, where students have to work autonomously, offering them a set of optional interactive quizzes with automated feedback may be a good teaching strategy to support them in their learning process. Within this framework, this paper investigates the relationship between optional quizzes and final exam performance in a calculus module. By means of multiple linear regression, this study found that an association exists between the learning achievement measured by final exam marks and participation in online quizzes together with the learning achieved through completion of these quizzes.