Recently, there have been efforts to rethink assessment. Instead of informing about (relatively stable) learner characteristics, assessment should assist instruction by looking at the learning process, facilitating feedback about what students' next step in learning could be. Similarly, new forms of strategy assessment aim at capturing self-regulated learning as it happens. One potential method for such assessment is the learning journal. We analyzed whether (a) quantity and (b) quality of learning strategies assessed by learning journals predict learning outcomes, and (c) whether differently successful combinations of strategies can be identified. In Study 1, 9th graders of medium-track high schools (N = 236) wrote learning journals in mathematics during 6 weeks. Foremost, quality and quantity of cognitive strategies predicted learning outcomes, controlling for prior knowledge. Learners who combined cognitive plus metacognitive strategies were particularly successful. Learners who mainly used 1 type of strategy performed similarly poorly as did learners who hardly used strategies. Study 2 in the domain of biology learning (N = 144) essentially replicated these findings. In summary, learning journals are a useful and innovative method for assessing learning strategies. (Contains 4 figures and 9 tables.)