Bring chicken broth and quinoa to a boil in a saucepan. Reduce heat to medium-low, cover, and simmer until quinoa is tender and water has been absorbed, 15 to 20 minutes.
Heat vegetable oil in a large skillet over medium-high heat. Saute onion and garlic in hot oil until onion is translucent, 5 to 7 minutes. Add ground chicken and break into small pieces while cooking until completely browned, 7 to 10 minutes.
Stir cooked quinoa and diced tomatoes into the chicken mixture; bring to a simmer and cook long enough for the flavors to meld, about 10 minutes more.