Discovery-based learning designs incorporating active exploration are common within instructional software. However, researchers have highlighted empirical evidence showing that "pure" discovery learning is of limited value and strategies which reduce complexity and provide guidance to learners are important if potential learning benefits are to be achieved. One approach to reducing complexity in discovery learning is limiting the range of possible actions for the learner to ensure that they do not undertake exploratory activities leading to confusion. This article reports on a study in which the learning outcomes from two learning conditions using computer-based simulations were compared. One condition allowed exploration through manipulation of simulation parameters, while the other allowed observation of simulation output from preset parameters, the latter condition designed to limit the complexity of the task. Learning outcomes for the 158 university student participants were assessed via pre-tests and post-tests of conceptual understanding. Students' exploration activities were recorded and their strategies subsequently coded as either systematic or unsystematic. The results showed that when compared with observation, systematic exploration resulted in learning benefits, while unsystematic exploration did not. These results have implications for the design of discovery learning tasks and instructional guidance within computer-based simulations.