Using quantitative methods, the current study addresses the phenomenon of blended learning and the impact of professional development (PD) in blended learning on teacher practice. Two separate but complementary investigations, Oliver's (2013) focus group data for examining Oliver's Framework for Blended Instruction and Parks' (2015) national open-ended survey results, unveiled a common thread, which provided motivation for this study. A purposeful sample of 366 secondary public school teachers located in the Southeastern United States completed the Blended Practice Profile, a self-assessment diagnostic instrument, to measure their practices in blended teaching. Results indicate contradictory data, demonstrating that the majority of participating teachers who self-identify as blended educators actually fell within the novice and emerging range for competency in blended instruction, concluding that blended learning is socially desirable and not fully understood in its entirety. The data illuminate a need for personalized professional development for teachers of blended instruction to meet their specific needs and gaps in understanding of the competencies necessary for effective blended pedagogy. The authors suggest that both formal and informal professional development should model blended instructional practices and techniques that focus on enhancing learning and measure for efficacy to successfully impact and transform blended instruction and behaviors in the classroom with fidelity.