Step 1

Preheat oven to 425°. Spread oats on a rimmed baking sheet and toast until lightly golden, about 6 minutes. Add pecans, toss to combine, and continue toasting until pecans are fragrant and oats are deep golden brown, about 6 minutes more. Let cool sightly.

Step 2

Whisk flour, salt, baking soda, cinnamon, and nutmeg in a medium bowl; stir in oats and pecans.

Step 3

Using an electric mixer on medium speed, beat butter, brown sugar, and granulated sugar in a large bowl, scraping down sides of bowl, until light and fluffy, 3–4 minutes. Add egg, syrup, and vanilla and beat until incorporated, about 1 minute. Reduce speed to low; add dry ingredients and raisins and continue to beat, scraping down sides and bottom of bowl, until just combined. Let sit at room temperature at least 1 hour to hydrate oatmeal.

Step 4

Preheat oven to 350°. Line 2 rimmed baking sheets with parchment paper. Using a 2-oz. ice cream scoop, portion cookies and place on sheets, spacing 3" apart (or measure out mounded scoops with a ¼-cup measuring cup). Do not flatten; cookies will spread as they bake.

Step 5

Bake cookies, rotating sheets halfway through, until edges are golden brown and firm but centers are soft, 15–17 minutes. Let sit on sheets 10 minutes, then transfer to wire racks; let cool.

Step 6

Do Ahead: Cookie dough can be made 3 days ahead; cover and chill. Let dough come to room temperature before baking.