Today’s high-tech consumer market demand complex, portable personal wireless consumer devices that are low-cost and have small sizes. Creative methods of combining mature integrated circuit (IC) fabrication techniques with innovative radio-frequency micro-electro-mechanical systems (RF-MEMS) devices has given birth to wireless transceiver components, which operate at higher frequencies but are manufactured at the low-cost of standard ICs. Oscillators, RF bandpass filters, and low noise amplifiers are the most critical and important modules of any wireless transceiver. Their individual characteristics determine the overall performance of a transceiver. This chapter illustrates RF-oscillators that utilize MEMS devices such as resonators, varactors, and inductors for frequency generation. Emphasis will be given on state of the art RF-MEMS components such as film bulk acoustic wave, surface acoustic wave, flexural mode resonators, lateral and vertical varactors, and solenoid and planar inductors. The advantages and disadvantages of each device structure are described, with reference to the most recent work published in the field.