We report on multiple photon monochromatic quantum oscillations (Rabi oscillations) observed by pulsed EPR (Electron Paramagnetic Resonance) of Mn 2+ (S=5/2) impurities in MgO. We find that when the microwave magnetic field is similar or large than the anisotropy splitting, the Rabi oscillations have a spectrum made of many frequencies not predicted by the S=1/2 Rabi model. We show that these new frequencies come from multiple photon coherent manipulation of the multi-level spin impurity. We develop a model based on the crystal field theory and the rotating frame approximation, describing the observed phenomenon with a very good agreement. 1. Introduction Quantum coherence of electron spin systems probed by pulsed EPR attracts a great interest due to its potential applications in quantum computation. Spin systems benefit from relatively large coherence and relaxation times, which makes them suitable as quantum bit implementations or as a new type of quantum random access memory [1, 2, 3, 4]. Recent studies show that the dilution of spins in diamagnetic hosts significantly reduces spin-spin dipolar interactions and allows spin quantum manipulations. Such situations are well exemplified by systems like N atoms in C 60 [5], NV centers in diamonds [6, 7] , Er 3+ [8, 9], Yb 3+ [10] and Cr 5+ [11] ions and molecular magnets[12, 13]. The majority of studies on electron spin qubits uses S=1/2 isotropic systems, which prevents strong static effects due to the crystal field or unwanted non linear effects. However, coherent manipulation of a multilevel system is needed as the first step towards the implementation of the Grover algorithm[14, 15, 16]. Although several quantum continuous wave (CW) EPR spectroscopy studies have been reported years ago[17], coherent multiple photon EPR (Rabi oscillations) have not been clearly demonstrated until recently [18].