We present high angular resolution images of the post-AGB nebula IRAS 18276-1431 (also known as OH 17.7-2.0) obtained with the Keck II adaptive optics (AO) system in its natural guide star (NGS) mode in the Kp, L p, and Ms near-infrared bands. We also present supporting optical F606W and F814W HST images as well as interferometric observations of the 12CO J = 1-0, 13CO J = 1-0, and 2.6 mm continuum emission with OVRO. The envelope of IRAS 18276-1431 displays a clear bipolar morphology in our optical and NIR images with two lobes separated by a dark waist and surrounded by a faint 4.5″ × 3.4″ halo. Our K p-band image reveals two pairs of radial "searchlight beams" emerging from the nebula center and several intersecting, arclike features. From our CO data we derive a mass of M > 0.38(D/3 kpc)2 M⊙ and an expansion velocity Vexp = 17 kms-1 for the molecular envelope. The density in the halo follows a radial power law ∝r-3, which is consistent with a mass-loss rate increasing with time. Analysis of the NIR colors indicates the presence of a compact central source of ∼300-500 K dust illuminating the nebula in addition to the central star. Modeling of the thermal IR suggests a two-shell structure in the dust envelope: (1) an outer shell with inner and outer radius Rin ∼ 1.6 × 1016 and Rout ≳ 1.25 × 10 17 cm, dust temperature Tdust ∼ 105-50 K, and a mean mass-loss rate of M ≈ 10-3 M⊙ yr-1; and (2) an inner shell with Rin ∼ 6.3 × 1014 cm, Tdust ∼ 500-105 K, and Ṁ ∼ 3 × 10-5 M⊙ yr-1. An additional population of big dust grains (radius a ≳; 0.4 mm) with Tdust 150-20 K and mass M dust = (0.16-1.6) × 10-3 (D/3 kpc)2 M⊙can account for the observed submillimeter and millimeter flux excess. The mass of the envelope enclosed within Aout = 1.25 × 1017 cm derived from SED modeling is ∼1 (D/ 3 kpc)2 Ṁ. © 2007. The American Astronomical Society. All rights reserved.