There is an increased demand for useful measures that capture students' math learning during intervention. Similarly, there is an awareness of the importance of researchers observing guidelines for study quality in publishing intervention results, including information related to outcome measures. We investigated the characteristics of outcome measures to assist researchers and practitioners in selecting appropriate outcome measures for early numeracy interventions. We also explored the level of quality regarding how studies reported outcome measure information. To do this, we analyzed 94 outcome measures of math achievement across 25 kindergarten early numeracy intervention studies. Overall, studies met 84% of the quality indicators related to outcome measures. Fewer studies met the recommendation to include multiple measures (i.e., proximal and distal measures; 60%) or provide validity information about measures (39%). Ultimately, the results of this study provide researchers with valuable information for developing and selecting outcome measures to determine the effectiveness of early numeracy interventions.