In this paper we study compactifications of heterotic string theory on manifolds satisfying the ∂∂-lemma. We consider the Strominger system description of the low energy supergravity to first order in α ′ and show that the moduli of such compactifications are subspaces of familiar cohomology groups such as H 1 (T X), H 1 (T X ∨ ), H 1 (End 0 (V )) and H 1 (End 0 (T X)). These groups encode the complex structure, Kähler moduli, bundle moduli and perturbations of the spin connection respectively in the case of a Calabi-Yau compactification. We investigate the fluctuations of only a subset of the conditions of the Strominger system (expected to correspond physically to F-term constraints in the effective theory). The full physical moduli space is, therefore, given by a further restriction on these degrees of freedom which we discuss but do not explicitly provide. This paper is complementary to a previous tree-level worldsheet analysis of such moduli and agrees with that discussion in the limit of vanishing α ′ . The structure we present can be interpreted in terms of recent work in Atiyah and Courant algebroids, and we conjecture links with aspects of Hitchin's generalized geometry to heterotic moduli.