The in-plane scattering patterns from a complex dielectric grating were both numerically and experimentally studied in contrast to those from well-known metallic gratings. The incidence was the transverse electric or transverse magnetic wave of wavelength λ=660  nm. The grating profile was complex with a period Λ=7.0  μm, while the material was lightly doped crystalline silicon. Patterns of the electric field, magnetic field, and spatial intensity distribution were demonstrated at the normal (θ(i)=0°) and oblique (θ(i)=+30°) incidence. Electric and magnetic fields were presented in the near field as well as the far field. The measured power ratio within -90°≤θ(r)≤+90° was plotted. Their major peaks and the numerically obtained diffraction efficiency of 21 orders (-10≤m≤+10 or -15≤m≤+5) of diffracted waves occurred at the same θ(r). Other peaks and stair-like shoulders of major peaks also exhibited in spectra.