He joined other Texan Democratic candidates such as Hank Gilbert, Fred Head, and Maria Luisa Alvarado in speaking out against the proposed Trans-Texas Corridor at public hearings in the summer of 2006. During his 2006 race for Attorney General of Texas, he vowed to fight for the people of Texas against the large monopolistic oil, insurance and media conglomerates, saying he'd "Fight them until hell freezes over and then fight them on the ice." Much of his funding for his 2006 campaign came from contributions of $20 to $100 from low to medium income donors who met him during his 254 county whistlestop campaign tour or read about him on the blogs. His opponent, Republican incumbent Greg Abbott entered the race with over six million dollars in his campaign war chest. As the Democratic nominee for attorney general, Van Os took his campaign directly to the people. He pledged to visit all 254 counties in Texas during the 2006 election cycle. With his wife, Rachel Barrios-Van Os, who served as his campaign manager, he visited each courthouse and spoke on the courthouse square. His last five whistlestop were in Tarrant County on October 16, Dallas County on October 17, Harris County on October 18, Travis County on October 19 and his home county of Bexar on October 20. Local supporters joined him on the courthouse steps as he proclaimed his determination to "return Texas government back to the people" denouncing the "bought and paid for perversion of the American political process." In Tarrant, truckdrivers passing on the street, acknowledged him by honking their horns when they saw the signs with his campaign message "Message to Big Oil -- I'm coming after you." During much of 2006 gasoline prices had soared to a record of over three dollars a gallon and dipped rapidly a month before the general election by at least a dollar a gallon. Many people suspected that the timing of the rise and fall was due to political manipulation. Supporters of Van Os funded billboards in many counties in Texas with the following message: "Message to Big Oil - I'm coming after you!" His opponent, Abbott, received considerable money from insurance companies. Van Os vowed to use the office of the attorney general, if elected, to enforce the anti-trust provisions of the Texas and U.S. constitutions, especially regarding insurance company pricing. His other billboard message during the 2006 attorney general's race was: "Insurance Gougers - I'm coming after you!" He married Rachel Barrios-Van Os, a native of San Antonio.