Preheat oven to 350 degrees, and line two large cookie sheets with parchment paper.

Whisk flour, salt and baking powder together in a medium bowl. In a separate bowl, by hand or by mixer, beat butter until creamy. Add sugars and beat the mixture until fluffy, about 3 minutes. Beat in eggs, one at a time. Stir dry ingredients into butter-sugar mixture with a wooden spoon or a large rubber spatula. Stir in oats and chocolate chips.

Place dough onto parchment-lined cookie sheets by large spoonfuls (about 2 tablespoons each), leaving at least 2 inches between. Bake until cookie edges turn golden brown, 20 to 25 minutes. Slide cookies (on parchment) onto cooling rack. Let cool, and store in airtight container.

Makes 18 large cookies.