Differential interference contrast microscopy, imaging by interferometric superposition of two displaced beams passed through a transparent sample, is one of the most sophisticated methods in classical microscopy. Here we demonstrate a versatile electronically controlled variant using a liquid-crystal spatial light modulator that displays a diffractive optical element and steers the beam separation. The orientation and magnitude of the shear angle and the relative phase of the two interfering beams can all be varied at video rates. The technique is demonstrated by imaging polystyrene beads in immersion oil and a sample of red blood cells. The method expands the capabilities of previous implementations of differential interference contrast microscopy by its nonmechanical control over all imaging parameters.