A survey instrument was developed and administered to 1,222 K-12 mathematics and science teachers to measure their beliefs about and use of inquiry in the classroom. Four variables (grade level taught, content area taught, level of support received, and self-efficacy for teaching inquiry) were significantly correlated to two dependent variables, percentage of time that students are engaged in inquiry during a typical lesson and the perceived ideal percentage of instructional time that should be devoted to inquiry. Specifically, elementary school teachers reported using inquiry-based practices more than either middle-school or high-school teachers; similarly, elementary-school teachers believed such practices should be used more often. All groups, however, reported believing in an ideal percentage of time devoted to inquiry instruction that was significantly greater than their reported percentage of time actually spent on inquiry instruction. A disordinal effect was found between grade level taught and content area taught; at the elementary level, science teachers reported both an ideal and actual percentage of time on inquiry higher than those reported by the math teachers, while at the high school level math teachers reported both an ideal and actual percentage of time on inquiry higher than those reported by the science teachers. No correlations were found between typical and ideal percentage of time devoted to inquiry and subject matter content knowledge training, gender, years of teaching experience, or maximum degree earned.