1Spray large bowl with non-stick cooking spray.
Combine pretzels,marshmallows,oats and butterscotch chips in spray-coated bowl;set aside.
2Lightly spoon flour into measuring cup;level off. In medium non stick sauce pan combine flour,sugar,milk,and margarine;mix well.
Bring to a full boil over medium heat;boil vigorously 3 minutes,stirring constantly.
Remove from heat;stir in peanut butter until smooth.
Pour over pretzel mixture;stir just until combined.
Press mixture firmly in a ungreased 13"x9" pan.
Cut into bars.