  New observations are presented of four evolved objects that display long,
multi-year variations in their light curves. These are interpreted as good
evidence of their binary nature, with the modulation caused by the barycenter
motion of the evolved star resulting in a periodic obscuration by a
circumbinary disk. Although protoplanetary nebulae (PPNe) commonly possess
bipolar nebulae, which are thought to be shaped by a binary companion, there
are very few PPNe in which a binary companion has been found. Three of the
objects in this study appear to be PPNe, IRAS 07253-2001, 08005-2356, and
17542-0603, with long periods of 5.2, 6.9, and 8.2 yrs, respectively. The
binary nature of IRAS 08005-2356 has recently been confirmed by a radial
velocity study. Two samples, one of PPNe and the other of post-AGB star
candidates, are investigated for further evidence on how common is a
long-period light curve variation. Both samples suggest such light variations
are not common. The fourth object, IRAS 20056+1834 (QY Sge), is an obscured RV
Tau variable of the RVb subclass, with a long period of 3.9 yrs and pulsation
periods of 102.9 and 51.5 days. The period of this object is seen to vary by
2%. Evidence is presented for a recent mass ejection in IRAS 17542-0603.
