Preheat oven to 350F and line two large baking sheets with parchment paper, or silicone mat.
In a medium bowl, combine oats, whole wheat flour, flaxseed, baking soda, and salt. Set aside.
In large bowl, using stand mixer with paddle attachment or electric hand mixer, cream together sugars with softened butter. The coconut sugar takes a little longer to cream with the oil and butter, so make sure to cream about 2 minutes, until coconut sugar crystals are less noticeable. (do NOT use melted oil and butter)
Add in egg and vanilla until combined.
Add dry oat and flour mixture to large bowl of wet ingredients and combine until dough comes together.
Using large wooden spoon, add in dried mixed berries. (Or use stand mixer paddle)
Using large cookie scoop (or rounded tablespoon) scoop dough balls and place on prepared cookie sheets, leaving about four inches of room between. Flatten dough just slightly (see second picture in post). The cookies will spread just slightly (as long as you weren't using melted butter).
Bake cookies for 8-10 minutes. Allow cookies to cool on baking sheet for 1 minute before transferring to wire rack to cool completely.
Store cookies in airtight container. Cookies will stay fresh up to one week (if they last that long).