Preheat oven 350 degrees. Grease a 9x13 inch metal baking pan. (Line with foil or parchment if desired)
Combine the flour, both sugars, salt and baking soda in bowl of a food processor and pulse to mix. Add butter and pulse until mixture is coarse and crumbly. Add oats and pulse to mix.
Press about 2/3 of the crumb mixture into the pan and set remainder aside. Bake crust for 12 minutes. Meanwhile, prepare filling.
Whisk the condensed milk, lemon juice, lemon zest and egg yolks together in a medium bowl and let stand for 5 minutes.
Arrange blueberries evenly over the crust; pour lemon mixture over the blueberries. Spread gently with a spatula to distribute as evenly as possible. Bake until the lemon mixture just begins to form a shiny skin; 7 to 8 minutes.
Sprinkle reserved topping over the lemon layer, then sprinkle pecans over topping. Bake for 25 minutes.
Let the bars cool in the pan on a rack until just warm, about an hour. When cool, transfer to refrigerator to chill for at least 2 hours. The longer the chill time, the better they’ll be.
Cut into about 24 bars