Romney visited the K.P. Kauffman Co., an oil and gas production and drilling company active in Rocky Mountain states.
This was his first 2012 campaign appearance in Colorado since February's caucuses.
Romney last appeared in Colorado on Feb. 7, the night of the Republican presidential precinct caucuses. Romney won Colorado's caucuses in 2008, but this year he lost Colorado to former Pennsylvania Sen. Rick Santorum, who has since left the race.
His wife, Ann Romney, will do a fundraiser in Denver on May 18.