Attune, which had $15 million in 2011 revenue, makes and markets a variety of cereals and snacks that are natural, organic, gluten free or free of genetically modified organisms. Its brands include Uncle Sam, New Morning, Attune, Skinner's and Erewhon. The company, led by CEO Rob Hurlbut, will continue to operate independently with the same team in San Francisco, according to information on the company's website. Post officials have not announced the deal.

"Attune Foods is strengthening our commitment to healthy living, whole grains, the gluten-free community and the Non-GMO Project with a new owner, Post Foods," says a statement on the Attune website. "...we wanted to be transparent about our newest supporters. Everything else stays the same: our people, products, recipes, ingredients and trusted certifications. In fact, our independent spirit and deep-rooted commitment to the natural foods industry is what attracted Post."