Differential Stroemgren uvby photometric observations from the Four College Automated Photoelectric Telescope are presented for the magnetic CP stars 45 Leo, HR 4330, 49 Her, and HR 6718. We refined Winzer's periods for 45 Leo and HR 6718 to 1.443820 days and 0.51899days, respectively. For HR 4330 our period of 3.516 days is quite different from that of Winzer. That for 49 Her, 0.93663days, is an alias of Winzer's.