The "Full House" star put her equestrian skills on full display this week in Spain -- riding 2 horses -- for the Global Champions Tour going down right now in Spain ... and she definitely looks the part.

MK rocked white jodhpurs with a black cropped jacket and black riding boots as she hopped on the backs of her trusty steeds, Fatum and Naomi

She soared over fences quickly enough to guide Naomi to a sixth-place finish at the tournament at Club de Campo Villa in Madrid.

The Olsen twin started riding horses when she was only 6 years old, but she took a break when she went to college at NYU ... and now she's building a new name for herself in the equine world.

Mary-Kate ... child actress, fashion mogul and horseback riding star!!!