This study investigated (1) the extent of vocabulary learning through reading and listening to 10 graded readers, and (2) the relationship between vocabulary gain and the frequency and distribution of occurrence of 100 target words in the graded readers. The experimental design expanded on earlier studies that have typically examined incidental vocabulary learning from individual texts. Sixty-one Taiwanese participants studied English as a foreign language (EFL) in an extensive reading program or in a more traditional approach structured around a global English course book. A pretest, posttest, and delayed posttest were administered to all participants. The results indicated that vocabulary gains through reading and listening to multiple texts were high. Relative gains were 44.06% after reading the 10 graded readers and 36.66% three months later. The relationships between vocabulary learning and frequency and distribution of occurrence were found to be non-significant, indicating that frequency was perhaps one of many factors that affected learning.