We propose a simple semiconductor optical amplifier–based fiber laser configuration for achieving multiwavelength oscillation at room temperature, in which a few-mode fiber Bragg grating was used as the wavelength-selective component. An amplitude variation of over a period was obtained for triple-wavelength oscillation at room temperature, which is more stable than that of erbium doped fiber (EDF)–based fiber laser with similar configuration. This multiwavelength laser can be switched between dual- and triple-wavelength operations by properly adjusting the polarization controller in the cavity. The lasing wavelength could be effectively tuned using the thermal heating method, and the output power variation was very small compared with that of the EDF-based fiber laser. This multiwavelength laser has the advantage of simple configuration, good stability, and wavelength tuning with small output power variation.