Heat oven to 350°F (180°C). Heat oil in skillet over medium-high heat.
Cook chicken for 4 to 6 minutes until no longer pink. Stir in salsa, 1/4 cup (50 mL) water, chili powder, oregano and salt.
Reduce heat to low and simmer uncovered for 5 minutes until thickened.
Heat shells according to package directions. Fill shells with chicken filling, taco sauce or salsa and toppings.
