We present a technique for obtaining a rigorous solution to the problem of diffraction of a plane electromagnetic wave by an infinite dihedral wedge with a magnetodielectric-coated cylinder at the apex. In the case of an E-polarized incident wave, we obtain a closed-form solution of the problem and present the results of exact calculations of the far-zone diffracted field for wide ranges of the structure parameters. In particular, it is shown that if the wedge apex is loaded with only a magnetodielectric cylinder, then the diffracted field for the very long-wavelength incident wave is not affected by the dielectric permittivity of the cylinder and the wave-incidence angle, but is affected only by the opening angle of the wedge, the diameter of the dielectric coating in terms of the free-space wavelength, the magnetic permeability of the coating, and the electric properties of the surrounding medium. If a half-plane or a wedge-shaped part are added to a single cylinder, then the backscattering coefficient of such a structure decreases, but the discovered resonance variation in the backscattering coefficient of the cylinder in the long-wavelength range becomes more pronounced.