The Epsilon Quadrant is the location of the magnetic void (TOS: "Lost Planet of the Gods, Part I"), as well as Kobol (TOS: "Lost Planet of the Gods, Part II"). The Battle at Galaxy's Edge takes place in an unnamed star system, located in the direction of Star Quadrant Epsilon seven mark four (TOS: "The Hand of God").
It is in proximity of Otarsis Quadrant, where Galactica's probe lead by Lieutenant Boomer discovers a Cylon listening post (TOS: "Lost Planet of the Gods, Part I").
Epsilon Quadrant is also the location of Arcta (TOS: "The Gun on Ice Planet Zero, Part I").