The Q(4) and R(4) branch features of the (0,0)D (5)Delta(4)-X (5)Delta(4) band system and the Q(3) and R(3) branch features of the (0,0)D (5)Delta(3)-X (5)Delta(3) band system of iron monoxide FeO have been studied by optical Stark spectroscopy. The Stark splittings in the high resolution laser induced fluorescence spectra were analyzed to produce values for the magnitude of the permanent electric dipole moments \mu\ of 4.50+/-0.03, 4.29+/-0.05, 2.53+/-0.04, and 2.58+/-0.06 D for the X (5)Delta(4) (v=0), X (5)Delta(3) (v=0), D (5)Delta(4) (v=0), and D (5)Delta(3) (v=0) states, respectively. The results are compared to several ab initio predictions and to FeC. The qualitative trends are explained in terms of a molecular orbital correlation picture. (C) 2004 American Institute of Physics.