Given that early career elementary teachers face pressure to plan pedagogy that provides equitable opportunities to learn mathematics for understanding, it is important to consider their mathematics lesson planning practices. This study uses interview data to compare the planning practices of four early career teachers (ECTs) who consistently rated highly on an observational measure of high-quality mathematics instruction with those of three ECTs who consistently rated lower. ECTs who scored highly addressed planning challenges in interconnected ways that were responsive to students' needs, demonstrated more agency in representing mathematics content in their planning, and were more likely to maintain curricular rigor when differentiating. We consider implications for efforts to help ECTs plan lessons that are likely to result in high-quality instruction.