These 4 packets and matching flashcards will help your students review the 4 vowel pairs: OU, OW, OI, and OY.
Looking for something more? You might be interested in the following:
Vowel Pairs - OU and OW - Lesson Packet
Vowel Pairs - OI and OY - Lesson Packet
Review & Test - Vowel Pairs - OU OW OI OY