Unique physical properties of granular soft ferromagnetic metal-dieleetric matrix nanocomposite materials (SF MMCs) make them very attractive in designing of magnetoelectronic devices. The most essential characteristics of GNMs are discussed in the chapter within the frame of percolation models, that establish correlation between microstructure and carrier transport mechanisms in MMCs. The chapter summarizes experimental results on tailoring of structure, magnetic, transport, and magnetotransport properties of (FeCoZr)(x) (Al2O3)(1-x) (17 at.% < x < 65 at.%) nanocomposite films by variation of metallic fraction and oxygen incorporation. Applied research techniques are alternation grads- and SQUID-magnetometry, atomic force microscopy/magnetic force microscopy (AFM/MFM), Mossbauer spectroscopy (MS), DC conductivity and magnetoresistance. Variations of the magnetic characteristics (coercivity fields, magnetization, MFM magnetic contrast) and carrier transport mechanisms due to incorporation of oxygen into FeCoZr-Al2O3 axe discussed with regard to the formation of complex semiconductive FeCo-oxide interlayers and/or shells possessing different types of magnetic ordering.