The three-year contract was awarded after a four-way pitch last month (Event, June). Opex previously held the tied contract and has retained seven shows, about 70% of its former business. It has gained the Spirit of Christmas Manchester show, which takes place at G-Mex from 28-30 November.
Clarion deputy managing director Kent Allen said: "With the portfolio continually broadening, we feel that we have split the business between Opex and EAG in a way that will benefit the company as a whole. We will continue the excellent relationship with Opex and profit from its knowledge and expertise.
"EAG will provide a fresh outlook on our shows and we feel both companies complement our progressive and dynamic culture."
Opex will continue to provide contractor services for shows including Top Drawer Autumn and Spring, House and Garden, and Olympia Show Jumping.
EAG has been appointed to cover exhibitions including The Baby Show London and Birmingham, Destinations London and Birmingham, and Caravan & Motor-home Manchester.
EAG chief executive Steve Barratt said: "I am very excited to be working with the Clarion team. To be awarded official contractor status is a great credit and confirms our commitment to delivering quality customer service."