From around 1522, he had gone to fight Amago clan along with his father, Yoshioki to win the control of Aki province. On 1528 upon Yoshioki's death, Yoshitaka became the head of Ouchi clan . In 1530s, he mainly led a military actions in the northern Kyushu defeating Shoni clan to win control of the area. With his back secure, from 1540 he again started combatting the Amago clan and by 1541, managed to completely control the Aki province.
However on 1542, an invasion into Izumo province ended in a disaster losing his adopted son Ouchi Harumochi along with large number of troops against Amago Haruhisa. He completely lost his ambitions of expanding his domains and devoted his energy to arts and cultures. His retainers split into two factions. Those led by Sagara Taketo wanted to the Ouchi clan to simply do nothing more than maintain the control of domains while those led by Sue Harukata wanted to continue expanding domains. Yoshitaka chose former as his advisors and on 1551, the faction led by Sue Harukata revolted to take over the Ouchi clan. With the control of troop in Harukata's hand, it was over in few days and Yoshitaka was forced to commit seppuku.
On those occasions that he led men into battles, he was actually a better than an average general but an unsuccesful invasion and loss of his adopted son made him lose his confidence and distrusting Sue Harukata who he personally did not like from beginning led to his downfall.