Heat oil in a medium saucepan over medium heat. Add quinoa and cook, stirring often, until golden, about 5 minutes. Add coconut milk, salt, and water and stir to combine. Bring to a boil; reduce heat, cover, and simmer until quinoa is tender and liquid is evaporated, 20–25 minutes. Stir in the grilled pineapple mixture and let sit 10 minutes. Fluff with a fork.