Magnesium atoms generated by laser ablation were reacted with methyl halides diluted (0.5% to 0.1%) in argon. Reaction products were trapped in a cryogenic argon matrix and analyzed by infrared spectroscopy. The primary reaction product, isolated Grignard molecule CH3MgX, and the secondary reaction products MgX, MgX2, MgH, MgH2, CH4, C2H6, CH2X, CH3MgCH3, XMgCH2, HMgCH3, and HMgCH2X were identified by isotopic (C-13, D, and Mg-26) substitution and by correlation with B3LYP and BP86 isotopic frequency calculations. This investigation reports the first experimental evidence for the fluoride Grignard species, CH3MgF. Infrared absorptions were also observed for associated Grignard species.