From Marshall Pass, walk north along the road until it begins to turn to the east and utilize trail if you want or head north into meadows with open forest to gain the broad south ridge that comes off Pt. 12,685. There is a short road that leads to a cabin near here that's two-tenths mile east of the pass summit. This road is just east of another 4WD road for the Colorado Trail. The cabin is called the "Hutchinson-Barnett" and is a public cabin, according to the Roach's. You can also begin your ascent from here.
If you stay more to the east side of this south slope/ridge, you can avoid denser forest and follow up on mostly open grass & tundra with open trees all about. The goal would be to gain the ridge where it forms up and becomes more pronounced south of PT. 12,685. On Google Earth you can even spot a trail now that goes all the way up to the ridge and beyond. Once on the ridge, the now more defined trail generally stays just on the west side, but at one point, goes off on the east side to avoid an area of rocks. The trail leads to the top of PT.12,685 where it then turns east for Mount Ouray. You'll lose just a little elevation as you walk east to a saddle, then begin the more arduous almost 1,400 foot ascent to the summit of Ouray. The hike will become increasingly rocky the higher you go, but the rocky terrain is never very difficult. Our children did just fine handling the conditions. There's one minor rock outcrop to avoid.
Once atop this isolated, high summit, you'll enjoy expansive views all around. Perhaps most impressive will be the view of the northern end of the Sangre de Cristo and of the San Luis Valley. Return by the way you came for a relatively easy descent.