 In 1887, he went to Paris to study at the Académie Julian under the French academic painters Tony Robert-Fleury and William-Adolphe Bouguereau.Trego studied at the French museums while he was there and enjoyed the Paris night life with other Pennsylvania Academy alumni such as Robert Henri, Augustus B. Koopman, Henry McCarter, and Frederick J. Waugh.Trego also participated in the Paris Salons of 1889 and 1890, gaining some recognition for his 1889 submission, a military painting titled "The End of the Charge of von Bredow’s Brigade at Rezonville" depicting German cavalry units charge against French during the Franco-Prussian War.