Lo's variation theory is a learning and teaching theory based on Marton's phenomenographic approach and is one of the most important backbones of learning studies. The proponents of variation theory demarcate their approach from constructivist learning approaches, stressing constructivism as philosophical framework, but not as learning theory. At the same time, the phenomenographic approach emphasizes the importance of Piaget's work about the cognitive development, which should be considered when talking about learning and teaching. We argue that -- from a theoretical point of view -- Piaget's theory of how cognitive schemata are developed and how variation theory proposes that learning can be fostered entails many similarities which are not apparent at first glance. We demonstrate the similarities and differences using a teaching example from an English as second language classroom and show the implications for practical instructional work. Finally, we discuss concrete suggestions how variation theory could benefit even more from Piaget's theory.