In a large bowl combine the flour, baking powder, salt, and oil. Gradually add the milk, stirring with a wooden spoon until absorbed. Continue stirring until a sticky ball of dough begins to form.
Remove the dough to a floured work surface and knead for about 2 minutes, or until the dough is soft and cohesive. Place the dough in a bowl and cover with plastic wrap and let rest for 20 minutes. Don't skip the resting!
Divide the dough into 16 equally sized portions. Roll each portion into a ball. Cover the balls with plastic wrap and let rest for another 10 minutes.
Take one ball of dough and flatten it with your hands. Using a floured rolling pin on a floured work surface, roll out the tortilla until very thin and about 8-inches in diameter. Keep the tortillas covered until ready to cook.
Heat a heavy, ungreased griddle or skillet over medium-high heat. Toss a tortilla onto the griddle and cook until brown spots begin to appear, about 1 minute. Use tongs to flip the tortilla and cook on the other side, about 1 minute longer. Transfer to a plate and finish the rest of the tortillas. Keep the tortillas stacked under a clean towel to keep warm. Serve or refrigerate the tortillas for up to 1 week or freeze in an airtight container for up to 2 months.
Notes
You can substitute half the flour with whole wheat flour. Also check out this recipe I posted long ago for homemade spelt flour tortillas.