Preheat the oven to 350F. Line 2 large baking trays with parchment paper or silpat liners.
Add the butter to a small skillet over medium heat. Let the butter melt and continue cooking until it turns light brown and smells nutty, about 5 minutes. Pour into a large bowl and let it cool until lukewarm.
Stir the brown sugar, egg, and vanilla into the browned butter.
Sift in the flour, cinnamon, salt, baking soda, and nutmeg.
Stir in the oats and pecans.
Divide the dough into 8 equal balls and arrange them on the prepared baking trays.
Bake until golden along the outside, but a touch doughy in the center, about 9 to 10 minutes, rotating the trays once halfway through. The cookies will harden as they cool.
Serve.
Notes
Nutrition information is for 1 cookie (they're very large!).
Tips to Make Chewy Cookies:
Use a slightly higher ratio of wet to dry ingredients