The reactions of magnesium atoms and methanol molecules have been investigated with matrix-isolation FTIR spectroscopy. In solid argon, the ground-state Mg atom reacted with methanol to form the Mg(CH3-OH) complex spontaneously on annealing. The complex underwent photochemical rearrangement to the methylmagnesium hydroxide (CH3MgOH) molecule upon ultraviolet-visible irradiation. The CH3MgOH molecule further reacted with a magnesium atom to form the CH3MgOMgH molecule. The aforementioned species were identified on the basis of isotopic IR studies with (CH3OH)-C-13, (CH3OH)-O-18, and CH3OD, as well as density functional theory calculations.