Elementary students' interest in science and careers in STEM are typically associated with their curiosity along with engagement in science activities and whether they find these activities to be fun, exciting, and enjoyable. Thus, early exposure of elementary students to STEM lessons must be engaging and enjoyable, which in turn increases the students' awareness and interests in these fields. Elementary school teachers are typically a major influence on their students' attitudes toward STEM. However, many elementary teachers have negative or unfavorable attitudes toward STEM areas. Consequently, many elementary students receive science instruction only a few days a week or only during some weeks of the year. This study aimed to enhance elementary teachers' interest, knowledge, and self-efficacy in teaching science that, in turn, will effectively build their students' interest in STEM areas. To accomplish this goal, we developed a PD program that consists of practice-based interventions with inquiry-based science curricula and instructional models. Then, we examined the effects of the interventions within the PD program, a practice-based summer workshop, and distance-based instructional coaching. We also investigated the effects of the instructional coaching delivered by two different types of coaches, peer elementary teacher vs. high-school science teacher, on the elementary teachers' inquiry-based instructional practices.