What is the letter in the following series AZEBIYO?

The series AZEBIYO consists of alternating letters from two sequences: the first sequence (A, E, I, O) consists of vowels, while the second sequence (Z, B, Y) consists of consonants. Following this pattern, the next letter after "O" (the last vowel) would be "R" from the consonant sequence since "R" follows "Y." Therefore, the next letter in the series is "R."