Lakeside is a city in Coos County, Oregon, United States. The population was 1,699 at the 2010 census. Lakeside is in Coos County, Oregon, …Lakeside is a city in Coos County, Oregon, United States. The population was 1,699 at the 2010 census. Lakeside is in Coos County, Oregon, along U.S. Route 101, about 1 mile inland from the Pacific Ocean. The city is 15 miles north of Coos Bay and 197 miles southwest of Portland.