In a medium bowl, whisk cinnamon, nutmeg, salt, baking soda, and flour. Set aside.
Cream butter and sugar in the bowl of a stand mixer fitted with the paddle attachment. (You can also use a large bowl and a hand mixer.) Cream until smooth, about 1-2 minutes. Mix in eggs, and vanilla and beat until smooth.
Gradually mix in dry ingredients until smooth, being careful not to over mix. Add oats and mix until all combined.
Peel, core, and chop your apples. Be sure to cut them small so they aren’t large chunks in your cookies. Stir apples into cookie dough.
Scoop 2 tablespoon sized balls of dough and place on a cookie sheet lined with parchment or wax paper. Cover with plastic wrap and chill for at least 30 minutes.
When ready to bake, preheat oven to 350°F. Line two cookie sheets with parchment paper or a silpat baking mat and place the cookie dough balls 2” apart.
Bake for 11-15 minutes, until the bottom is slightly golden. Cool on cookie sheets for 10 minutes, then remove to a rack to cool completely.
Store cookies in an airtight container for up to 4 days. They can also be frozen in an airtight container or ziploc bag for up to 2 months.