Although T-duality is an inherently stringy symmetry, it can be seen at the effective field theory level, both in the classical two-derivative action and at the alpha' corrected level. In fact, T-duality invariance can be a powerful tool in constraining the form of the alpha' corrections. A particularly interesting framework involves a cosmological reduction where all spatial dimensions are compactified on a torus. The resulting system only involves the generalized metric on the torus, giving rise to a generalized geometry approach to constructing T-duality invariants. We explore both tree-level R^2 and R^4 corrections in the cosmological reduction and highlight the role of the generalized connection with torsion in constructing higher-curvature invariants.