A method of making a reinforced insulating panel which includes the steps of covering insulating material, such as urethane foam of a regular size with glass fiber textiles, quilting the insulating material and the glass fiber textiles together so as to produce an integral middle member, covering the inner covering of the glass fiber of the middle member with an outer covering of the glass fiber and impregnating the covered member with a thermosetting resin and hardening the impregnated member. The glass fiber reinforced panel produced has excellent fire retardant and water repelling properties, has improved compressive strength and does not deform or delaminate easily.