We present a simple method for fully stabilized mid-infrared optical frequency comb generation based on single-pass femtosecond optical parametric generation that is seeded by a continuous-wave laser. We have implemented the method in a periodically poled lithium niobate crystal that produces a frequency comb tunable across 3325 nm-4000 nm (2380 cm-1-3030 cm-1). The method generates the mid-infrared (idler) comb with known and stabilized Carrier-Envelope Offset (CEO) frequency without the need to directly detect it. The idler CEO is continuously tunable for almost half of the repetition rate and can be modulated. Together with the high output power (up to 700 mW) and low intensity noise (0.018% integrated in 10 Hz-2 MHz bandwidth), this makes the demonstrated mid-infrared frequency comb promising for many applications such as high-precision molecular spectroscopy, frequency metrology, and high harmonic generation.