The Japanese star's 9-under round on a hot afternoon in the desert saw her into a two-stroke lead ahead of South Korean Jee Young Lee.
Tied for third a shot further back were Americans Brittany Lang and Gerina Piller, Chinese Taipei's Candie Kung and Thai Pornanong Phatlum.
Miyazato suffered whiplash injuries in a five-car crash on her way to the airport after a tournament in Thailand a fortnight ago, leading to her pulling out of the following weekend's tournament in Singapore.
In Arizona she pulled away late in the round, birdieing the par-3 14th, par-4 16th and par-3 17th while shooting an eagle on the par-5 15th.