Make the filling:

Heat oil in a medium pan and sauté bell peppers for 3 minutes over medium heat.
Add onions and cook for 3 more minutes or until translucent.
Add chicken, tomatoes, and mix well to combine.
Pour in chicken stock and season with garlic, chili powder, salt, and pepper to taste.
Cook stirring constantly until all juices are gone and vegetables are cooked through.
Transfer the mixture to a bowl, allow it to cool down.
Add cheese and mix to combine. Set aside.

Assemble taquitos:

If using corn tortillas, heat them up between damp paper towels in the microwave for 20-30 seconds. If using flour tortillas you won’t need to heat them.
In the middle of a tortilla add two or three tablespoons of the chicken and cheese mixture.
Roll tight and place the taquito seam side down on a plate.
Repeat with remaining tortillas and filling.

Bake:

Brush taquitos with a bit of oil on all sides, or use a cooking spray.
Brush a baking tray with oil and place all taquitos in a single layer.
Preheat your oven to 400°F (200°C) and bake the taquitos for 10-15 minutes, turn them once and keep baking until golden and crispy on all sides.

Serve:

Serve as an appetizer with various salsas on the side or as a main meal. Check the notes for the toppings and salsa options, then choose your favorites.