Any instructional practice must be derived from a teacher's knowledge base for teaching, which can be acquired by training, study, or practice. While much attention has been paid to teachers' practical content knowledge in real educational settings, comprehensive syntheses of expert knowledge on a particular teaching task for a specific group of teachers are still scarce. This paper tends to synthesize ESL/EFL teachers' pedagogical content knowledge of reading strategy instruction through learning the expertise conveyed in literature. Drawing on related studies in the field of reading strategy instruction either in general or in ESL/EFL contexts, this argumentative article first proposes a synthesized reading strategy instruction model which consists of one key component and two general principles, all of which create and are created by a safe and risk-free environment where students learn to use strategies actively and consciously with motivation and assistance. This article then elaborates on eight instructional strategies using summarizing strategy instruction as an example in terms of three types of knowledge: declarative, procedural, and conditional. With the enrichment of the pedagogical content knowledge on strategy instruction, ESL/EFL teachers might teach reading strategies effectively both "with" metacognition, i.e., consciously planning, monitoring, and evaluating their teaching, and "for" metacognition, namely, to affect their students' metacognitive awareness of strategy use in reading.