Heat oil in medium saucepot over medium-high heat. Add chorizo slices. Cook, stirring occasionally, until browned on both sides, about 2 minutes; transfer to plate. Stir in onions and garlic; cook until onions soften, about 2 minutes more.
Pour 2 cups water into pot; bring to boil. Stir in contents of box of yellow rice; return water to boil. Add chorizo; cover pot. Reduce heat to low. Simmer, covered, until water is absorbed and rice is tender, about 25 minutes, adding peas after 20 minutes. Serve warm.