Laser-ablated Si, Ge, and Sn atoms and electrons have been codeposited with CO in excess argon at 11 K. In addition to SiCO, GeCO, SnCO, and bent Si(CO)(2), Ge(CO)(2), and Sn(CO)(2) molecules, carbonyl anions as SiCO-, GeCO-, and SnCO- were produced via electron capture by the neutral carbonyls during cocondensation process. The anion species were identified by isotopic substitutions, CCl4 electron trapping, and density functional calculations. All these carbonyl anions are calculated to have (2)Pi ground state with linear geometry.