Adjust oven racks to upper- and lower-middle positions; heat oven to 350 degrees. Line 2 large (18 by 12-inch) baking sheets with parchment paper. In first bowl, whisk flour, baking powder, baking soda, and salt in medium bowl. In second medium bowl, stir together oats, pecans, cherries, and chocolate. In mixer with flat beater, beat butter and sugar on medium until no sugar lumps remain, about 1 minute. Scrape down sides of bowl; add egg and vanilla and beat on medium-low speed until fully incorporated, about 30 seconds. Scrape down bowl With mixer running at low speed, add flour mixture; mix until just combined, about 30 seconds. With mixer still running on low, gradually add oat/nut mixture; mix until just incorporated. Give dough final stir with rubber spatula to ensure that no flour pockets remain and ingredients are evenly distributed. Divide dough into 16 portions, each about 1/4 cup, then roll between palms into balls 2 diameter; stagger 8 balls on each baking sheet, spacing them about 2 1/2 inches apart. Gently press each dough ball to 1 inch thickness. Bake both baking sheets 12 minutes, rotate them front to back and top to bottom, then continue to bake until cookies are medium brown and edges have begun to set but centers are still soft (cookies will seem underdone and will appear raw, wet, and shiny in cracks), 8 to 10 minutes longer. Do not overbake. Cool cookies on baking sheets on wire rack 5 minutes; using wide metal spatula, transfer cookies to wire rack and cool to room temperature. We like these cookies made with pecans and dried sour cherries, but walnuts or skinned hazelnuts can be substituted for the pecans, and dried cranberries for the cherries. Quick oats used in place of the old-fashioned oats will yield a cookie with slightly less chewiness. If your baking sheets are smaller than the ones described in the recipe, bake the cookies in three batches instead of two. These cookies keep for 4 to 5 days stored in an airtight container or zipper-lock plastic bag, but they will lose their crisp exterior and become uniformly chewy after a day or so