A muntin clip for use with a spacer frame or window sash having an elongated channel extending around an inner periphery of the frame. The disclosed muntin clip has a spacer frame or sash engaging body for insertion into a channel of the spacer frame. A flexible body portion flexes from a first configuration to a second configuration as the clip is pushed into the spacer frame to exert an outward force against walls of the spacer frame bounding the frame channel. The disclosed clip also includes a muntin bar engaging body attached to the spacer frame engaging body that includes a flexible portion that flexes as the muntin bar engaging body is pushed into the muntin bar to frictionally engage the muntin bar.
