This paper presents an investigation of open-loop control of cavity flow oscillations using a three-dimensional (3-D) array of steady jets located at the leading edge of the cavity. The actuation is introduced to suppress flow oscillations in a rectangular cavity with a length-to-depth ratio (L/D) of 6 at Mach numbers from 0.3 to 0.7. Several different slot-jet configurations are assessed for their control performance considering the jet output momentum and interactions with the boundary layer at the leading edge. Significant tonal and broadband reduction of cavity oscillations are observed using 3-D actuation with wavelengths (λ/D) from 0.5 to 1 and with 25-50% spatial duty cycle. High speed (12 kHz) schlieren imaging and 2-D and Stereo Particle Image Velocimetry (SPIV) are performed to investigate the baseline and controlled flow fields. Companion 3-D large eddy simulations (LES) are performed and exhibit good agreement with the experiments. The experiments and complementary LES reveal detailed flow physics. The 3-D actuation introduces strong spanwise wave-like structures which disrupt the growth of the shear layer and reduce the strength of the impingement region. The experimental and numerical analysis aid in the development of optimal control methodologies.