Aurel Lazăr was a lawyer, a politician, and one of the most energetic supporters of the Romanian national cause in the Austro-Hungarian Empire.

He completed his legal studies in Oradea and Budapest. He was involved in politics beginning with 1901, upon becoming a member of the Executive Committee of the Romanian National Party. In order to disseminate his ideas, he began to collaborate with various newspapers and magazines, like Tribuna poporului (The Tribune of the People) and Românul (The Romanian). At the outbreak of the Great War, he was mobilised, but as he suffered from diabetes, remained at home. However, his involvement in the national struggle of Romanians continued.

On October 12, 1918, an important document was conceived during a meeting that took place in his house, namely the famous Oradea Declaration, which proclaimed the right to self-determination of the Romanians in Transylvania. He was actively involved in the preparation of the Great National Assembly of December 1, 1918. He was also a member of the Grand National Council of Alba Iulia and of the Directing Council, overseeing the Justice Department.

After the Union was accomplished, Lazăr continued to distinguish himself in the political scene of Greater Romania. He was a Member of Parliament between 1919 and 1930, representing the Romanian National Party and later its successor, the National Peasant Party. He also served as Deputy Chairman to the Chamber of Deputies (1928) and as Mayor of Oradea (1930).