This study used a post-test-only control group experimental design to determine the effects of prelecture online quizzes on the students' perceived preparation and academic performance. The participants included 54 pre-service Turkish teachers of English enrolled at a state university in Turkey. The participants were randomly selected from a list and were assigned to two sections: control and experimental groups. The students in the control group were not required to take the online quizzes, while the ones in the experimental group were asked to complete the pre-lecture online quizzes. The results showed that the participants in the experimental group scored higher on the final examination at the end of the semester than those in the experimental group and that a significant positive correlation existed between the scores on the quizzes and the scores on the final examination. Moreover, the participants in the experimental group reported that they prepared for the classroom discussions having learnt the key terms and concepts since the online quizzes urged them to do the required readings.