First-principles calculations based on the tight-binding linear muffin-tin orbital (TB-LMTO) method are performed to investigate the occurrence of spin polarization in the alkali-metal oxides (M2O) [M: Li, Na, K, Rb] in antifluorite (anti-CaF2-type) structure with non-magnetic sp (F, Cl, Br and I) dopants. The calculations reveal that non-magnetic substitutional doping at cation site can induce stable half-metallic ferromagnetic ground state in I-2-VI compounds. Total energy calculations show that the antifluorite ferromagnetic state is energetically more stable than the antifluorite non-magnetic state at equilibrium volume. Ground state properties such as equilibrium lattice constant and bulk modulus were calculated. The calculated magnetic moment is found to be 2.00 mu B per dopant atom.