Miniaturized, multi-band and high frequency oscillators that are compatible with CMOS processes are highly desirable for the synthesis of compact, stable, and low power frequency sources for reconfigurable radio frequency communication systems and cognitive radios. Aluminum nitride (AlN) contour mode MEMS resonators (CMR) are emerging devices capable of high Q, low impedance, and multi-frequency operation on a single chip. The frequency stability of these AlN MEMS devices is of primary importance in delivering oscillators that exhibit low phase noise, and low sensitivity to temperature and acceleration. In this article we describe how the resonator dynamics impacts oscillator performance and present some preliminary demonstrations of ultra-high-frequency (UHF) oscillators. An example of an oscillator prototype we synthesized with a 586 MHz AlN CMR exhibited phase noise < - 91 dBc/Hz and - 160 dBc/Hz at 1 kHz and 10 MHz offsets, temperature stability of 2 ppm from - 20 to + 85 C, and acceleration sensitivity < 30 ppb/G.