ST. LOUIS — Ron Shaich, founder and executive chairman of Panera Bread Co., and Bill Moreton, president and chief executive officer, will become co-c.e.o.s of Panera, effective immediately. Panera said the transition to co-c.e.o.s formalizes a relationship that has evolved over the past year and is a reflection of the way in which Mr. Shaich and Mr. Moreton have been operating as partners. Mr. Moreton, who joined Panera in 1998, succeeded Mr. Shaich as president and c.e.o. in May 2010. At that time, Mr. Shaich was named executive chairman and said he planned to “take what I have learned at Panera to the broader world.” Mr. Shaich began his career in the bakery-cafe industry in 1981 and went on to co-found Au Bon Pain Co., Inc. and, ultimately, co-found Panera Bread.