Lightly spray an 8x8-inch baking pan with cooking spray.

Place Chex in a sealable plastic bag and crush slightly with a rolling pin or by hand. In a large bowl combine crushed Chex, Cheerios and sunflower seeds.

In 3-quart saucepan, over medium-high heat, heat honey, sugar, cinnamon and vanilla just to boiling, stirring occasionally. Remove from heat and stir in peanut butter. Pour over cereal mixture and stir gently until evenly coated.

Press mixture into prepared baking pan. Refrigerate 1 hour or until set. Cut into 8 bars. Store covered at room temperature for up to 1 week.