Line a 8x8 baking pan with aluminum foil. Spray lightly with non-stick cooking spray. Set aside.

Place peanut butter and honey in a large, microwave safe bowl. Heat on high for 1 minute. Stir until completely smooth. Stir in oats. Let cool slightly, then stir in half of the M&M's.

Press batter in prepared pan. Use a spatula to make batter smooth on top. Pour remaining M&M's on top and press gently. Place in refrigerator until set, about 30 minutes to an hour. Cut into squares.

Serve immediately or store covered in refrigerator to keep firm.