He relocated to the town of Edmonton in 1892, becoming the town's first architect. He also operated a brickyard upon settling. In 1892, Edmiston, working independently at the time, was contracted by the Edmonton Town Council to draft a map of the town. In that same year, he was also a member of a committee tasked with a project to establish a brewery in Edmonton. In 1893, he established a partnership with local architect Nathaniel G. Flater, and operated under the name Edmiston & Flater, headquartered at the Edmonton Imperial Bank Building. The firm designed many notable buildings for the town, including the first post office, the city's first brick school (for the Edmonton Public School District), the All Saints' Anglican Cathedral, a home for Herbert Charles Wilson, the McDougall & Secord retail store, and a fire hall. In 1899, he would end his partnership with Flater and enter into a new one, with Henry D. Johnson of Calgary, under the firm name Edmiston & Johnson Architects, Draughtsmen, Valuators and Insurance Agents. This firm was responsible for constructing, amongst many, a hospital building, a new Presbyterian church and making alterations to the Robertson Hall Theatre.