Steinberg purchased the Grand Union chain of 38 stores in June 1959 to make its entrance into the Ontario market. These stores operated unter the Steinberg banner until 1969. In January 1969, the marketing program of "Miracle Discount Pricing" was introduced and the entire chain of stores was converted to the Miracle Food Mart banner. The marketing philosophy was a simple one, reduce all of the "fancy" advertising such as colour flyers, television and radio spots and offer everyday items at deeply reduced prices as a line item within the weekly black & white flyer. This move proved to be successful as the chain expanded quickly (to approximately 80 stores) over the next ten years, gaining a substantial increase in market share.
In 1973, the Miracle Food Mart division made a revolutionary move to abolish its general-image advertising and to mount a "give-'em-the-facts" consumer-oriented campaign. The program included a formal Consumer Bill of Rights, nutrition booklets, a key to the codes used to mark perishables, and clearly labelled price tags.
The supermarket flourished in the 1970s, and expanded with the Miracle Ultra Mart banner into bigger stores with a wide range of health care and general merchandise. The company spent C$30 million in improvements for its Miracle Food Marts in 1987, creating several large 24-hour food-and-drug stores called Miracle Ultra-Marts. The stores offered fresh fish and deli departments, party-planning services, kitchen centers selling microwave ovens, and hardware and electronic centers. In 1989, the chain was sold to A&P Canada. A&P converted the Miracle Food Mart stores into A&P, Dominion or Food Basics stores, but continued the Ultra Mart banner (dropping the "Miracle"), which it later rebranded as Ultra Food & Drug.
Miracle Food Mart stores were often paired with Miracle Mart discount department stores (another Steinberg chain) in mall settings, but in the latter years, they became stand-alone locations at smaller plazas across the Greater Toronto Area.