At the age of 16, Dallas received the Sarah Exley Scholarship, awarded to one American student every three years in support of their study of acting at the prestigious Mountview Conservatoire for the Performing Arts in London, England. In London, at the age of 20, he landed his first professional job as an actor with the acclaimed Royal Shakespeare Company, and he went on to perform with some of the most renowned theatrical companies in the world, including the Royal National Theatre, The English National Opera, The New Shakespeare Company and The Young Vic.
Though he never left the theatre far behind, Dallas began to land parts in television and independent features. Feeling nostalgic for his home after a decade abroad, he made the move back stateside and landed in Hollywood. Five days later he received a call offering him the leading role of Fandral in 2011's Blockbuster Thor, directed by the Oscar-nominated director/actor Kenneth Branagh.