Part I of this study examined the effect of two 9-week instructional climates (low autonomy [LA] and mastery motivational climate [MMC]) on object-control (OC) skill development in preschoolers (N = 117). Participants were randomly assigned to an LA, MMC, or comparison group. OC skills were assessed at pretest, posttest, and retention test with the Test of Gross Motor Development-2nd Edition. A significant Treatment x Time interaction (p less than 0.001) was present, supporting the effectiveness of both OC instructional climates in improving OC skills over time, while the comparison group resulted in no changes. The authors conclude that developmentally and instructionally appropriate climates are beneficial to OC skill learning, along with the need for "planned" movement experiences in motor learning environments. (Contains 1 figure.)