There are 3 12-letter words that start with 'moo'.
| moonchildren | moonlighters | moonlighting | 
Note: These 3 12-letter words that start with 'moo' are found from the USA & Canada version of the tournament Scrabble word list.
Also see words start with moon, moor, mood, mool, moot, mooc, moos, mooe, mooi.
4-letter words start with 'moo' (6)