We report the results of an alternate form reliability and criterion validity study of kindergarten and grade 1 (N = 84-199) reading measures from the easyCBM© assessment system and Stanford Early School Achievement Test/Stanford Achievement Test, 10th edition (SESAT/SAT-­10) across 5 time points. The alternate form reliabilities ranged from 0.31-0.94 for the kindergarten measures and from 0.27-0.96 for the grade 1 measures. Multiple regression analyses were used to examine the overall variance explained by the combined measures when predicting end-of-­year reading achievement. In kindergarten, the easyCBM© measures accounted for 35-58% of the variance in SAT-10 performance. In grade 1 easyCBM© measures accounted for 14-32% of the variance in SAT-10 performance and 49-­56% of the variance in performance on the easyCBM© word reading fluency measure administered at time 5.