Combine pecan halves and corn syrup, stirring to coat pecans. Line a 15- x 10-inch jellyroll pan with parchment paper or aluminum foil; coat with cooking spray. Arrange pecan halves in an even layer in pan.
Bake at 350° for 12 minutes; stir using a rubber spatula. Bake 8 more minutes. Remove from oven, and stir; arrange in an even layer on wax paper, and let cool completely.