X0306 4 2018-05-15 0001466593 Otter Tail Corp OTTR 0001191492 MOUG KEVIN G 215 S CASCADE ST FERGUS FALLS MN 56537-2801 1 CFO & Sr VP Common Stock 2018-05-15 4 S 0 1500 43.4776 D 56516 D Common Stock 172 I By Daughter Common Stock 172 I By Daughter Common Stock 314 I ESOP The sale reported on this Form 4 was effected pursuant to a rule 10b5-1 Sales Plan adopted by the reporting person on June 27, 2017. The price reported is the weighted average sale price for the transaction reported. The prices received ranged from $43.30 to $43.65. The reporting person will provide to the issuer, a security holder of the issuer, or the SEC staff, upon request, full information regarding the number of shares sold at each price within the range. Total direct holdings include shares jointly held with spouse, shares acquired individually through the Employee Stock Purchase Plan and shares acquired pursuant to Restricted Stock Awards and Performance Award distributions. /s/ Kevin G Moug by Ella Leapaldt, Attorney-in-Fact 2018-05-16