Traditional microbiology laboratory activities tend to focus solely on skill development, leaving untapped the great potential for students' deep understanding of underlying fundamental microbiology concepts. To address this issue, I present an inquiry-based instructional sequence for a common skill-based lab in undergraduate majors' and non-majors' biology: the Gram stain. The modified lab includes elements of inquiry without completely overhauling the original activity to allow for both skill-based and conceptual knowledge development. With a few alterations, this instructional sequence could easily be tailored to suit similar microbiology labs. This instructional sequence could also be used to modify biology labs into inquiry lessons at any grade level.