Abstract. We show here that the spectrum of the family of noncommutative harmonic oscillators Q w (α,β) (x, D) for α, β ∈ R+ in the range αβ = 1, is [0, +∞) and is entirely essential spectrum. The previous existing results concern the case αβ > 1 (case in which Q w (α,β) (x, D) is globally elliptic with a discrete spectrum whose qualitative properties are being extensively studied), and ours therefore extends the picture to the range of parameters αβ ≥ 1.