As a member of the Union of the Democratic Centre (UCD) he was elected to the Constituent Cortes and the Senate in the Spanish transition to democracy.
He was Vice President of the Government of Aragon from 1999 to 2011, in coalition with the Spanish Socialist Workers' Party (PSOE) under Marcelino Iglesias.
He began his political career during the Spanish transition to democracy as a member of the Union of the Democratic Centre (UDC), being elected as a deputy in the Constituent Cortes in 1977 and to the first Senate in 1979.
In 1987, he became an advisor in the government of PAR president Hipólito Gómez de las Roces, retaining his position under successor Emilio Eiroa four years later.
This lasted for three legislatures until 2011, when the PP won under leader Luisa Fernanda Rudi and formed a coalition with the PAR; Biel became President of the Cortes, the speaker.