Molecular oxygen (O2) is extremely important for a wide variety of processes on and outside Earth. Indeed, O2-He collisions are crucial to model O2 abundance in space or to create ultra-cold O2 molecules. A crossed molecular beam experiment to probe rotational excitation of O2 due to Helium collisions at energies of 660 cm-1 is reported. Velocity map imaging was combined with state-selective detection of O2(X3∑_g^-) by (2+1) resonance enhanced multi-photon ionization. The obtained raw O2+ images were corrected from density to flux and the differential cross sections (DCS) were then extracted for six O2 final states. Exact quantum mechanical calculations were also performed. A very good agreement between experimental and theoretical DCSs was found using an initial O2 beam population ratio of 80% for the first rotational state and 20% for the first excited state. The agreement demonstrates our ability to model inelastic processes between O2 molecules and rare gas.